This document provides information on solutions of non-electrolytes. It defines key terms like solute, solvent, saturated solution, and supersaturated solution. It explains how a solution forms via a 3 step process of solute separation, solvent separation, and solute-solvent interaction. Various methods of expressing concentration are described, including mass percentage, parts per million/billion, mole fraction, molarity, molality, and normality. Raoult's law and its limitations are discussed. Real solutions that deviate positively or negatively from Raoult's law are explained. Henry's law relating gas solubility to partial pressure is also summarized.
Surfactant is a surface active agent which are used to prevent surface tension and interfacial tension. It is important prevent interfacial fluidity, it is amphiphilic molecule having Hydrophilic head and Lipophilic tail. It is important for poorly water soluble drug and it is important to influencing water solubility of poorly water soluble drug. It is important to prevent the inter and intra subject variability.
It act as solubilizing agent, suspending and emulsifying agent, stabilizing agent, wetting agent, detergent, Foaming agent.
It is important for preparation of Nanoemulsion, Nanosuspension, Microemulsion.
It is important to show antibacterial as well as antimicrobial activity.
It is important for Novel drug delivery system, oral drug delivery system, Targeted drug delivery system.
It is important to influencing oral bioavailability of poorly water soluble drug.
The movement of molecules from one phase to another is called partitioning.
If two immiscible phases are placed adjacent to each other, the solute will distribute itself between two immiscible phases until equilibrium is attained; therefore no further transfer of solute occurs.
Volumetric Analysis
Types of titration
Acid- Base Theory
Reaction, End Point & Indicators
Acid- Base titration
Titration curve
Non- Aqueous Titration
Precipitation Titration
Complexometric Titration
Oxidation- Reduction Titration,
Calculation. Errors
General Informations,
State of matter and properties of matter (Part-7)(Solid-crystalline, Amorpho...Ms. Pooja Bhandare
CRYSTALLINE SOLID, Types of Crystalline solid, AMORPHOUS SOLID, Difference between crystalline solid and amorphous solid, Why does the amorphous form of drug have better bioavaibility that crystalline couterpaerts?, Polymorphism,
TYPES OF POLYMORPHISM, PROPERTY OF POLYMORPHS, Methods of preparation of Polymorphs, Methods to determine Polymorphism Characterization of Polymorphs, Pharmaceutical Application
Definition of reaction kinetics, law of mass action, rates of reaction- zero, first, second, pseudo zero & pseudo first order reaction, molecularity of reaction, determination of reaction order- graphic method, substitution method, half life method.
Surfactant is a surface active agent which are used to prevent surface tension and interfacial tension. It is important prevent interfacial fluidity, it is amphiphilic molecule having Hydrophilic head and Lipophilic tail. It is important for poorly water soluble drug and it is important to influencing water solubility of poorly water soluble drug. It is important to prevent the inter and intra subject variability.
It act as solubilizing agent, suspending and emulsifying agent, stabilizing agent, wetting agent, detergent, Foaming agent.
It is important for preparation of Nanoemulsion, Nanosuspension, Microemulsion.
It is important to show antibacterial as well as antimicrobial activity.
It is important for Novel drug delivery system, oral drug delivery system, Targeted drug delivery system.
It is important to influencing oral bioavailability of poorly water soluble drug.
The movement of molecules from one phase to another is called partitioning.
If two immiscible phases are placed adjacent to each other, the solute will distribute itself between two immiscible phases until equilibrium is attained; therefore no further transfer of solute occurs.
Volumetric Analysis
Types of titration
Acid- Base Theory
Reaction, End Point & Indicators
Acid- Base titration
Titration curve
Non- Aqueous Titration
Precipitation Titration
Complexometric Titration
Oxidation- Reduction Titration,
Calculation. Errors
General Informations,
State of matter and properties of matter (Part-7)(Solid-crystalline, Amorpho...Ms. Pooja Bhandare
CRYSTALLINE SOLID, Types of Crystalline solid, AMORPHOUS SOLID, Difference between crystalline solid and amorphous solid, Why does the amorphous form of drug have better bioavaibility that crystalline couterpaerts?, Polymorphism,
TYPES OF POLYMORPHISM, PROPERTY OF POLYMORPHS, Methods of preparation of Polymorphs, Methods to determine Polymorphism Characterization of Polymorphs, Pharmaceutical Application
Definition of reaction kinetics, law of mass action, rates of reaction- zero, first, second, pseudo zero & pseudo first order reaction, molecularity of reaction, determination of reaction order- graphic method, substitution method, half life method.
Electrolytes also known as polar molecules are bonded by ionic bond. They conduct electricity in molten or dissolved state.TatvaChintan Pharma Chem is a renowned company that manufactures electrolytic chemicals.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
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(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
2. What is a solution?
• A solution is a homogeneous mixture
• A solute is dissolved in a solvent.
• Solute is the substance being dissolved
• Solvent is the medium in which the solute dissolves
• An aqueous solution has water as solvent
2
3. SATURATED – contains the
max. no. of solute that
dissolves at that temperature
SUPERSATURATED –
Contains more than is
possible and are unstable
Unsaturated solution Saturated solution
Solution
Unsaturated Saturated
Supersaturated
3
4. Super saturated solution
Solvent holds more solute than is normally possible
at that temperature.
These solutions are unstable; crystallization can
often be stimulated by adding a “seed crystal” or
scratching the side of the flask.
4
5. How Does a Solution Form?
1. Solvent molecules attracted to surface ions.
2. Each ion is surrounded by solvent molecules.
3. Enthalpy (DH) changes with each interaction broken or
formed.
5
6. It is a 3 step process
1. Separation of Solute
• Must overcome IMF or ion-ion attractions in solute
• Requires energy, ENDOTHERMIC ( + DH)
2. Separation of Solvent
• Must overcome IMF of solvent particles
• Requires energy, ENDOTHERMIC (+ DH)
3. Interaction of Solute & Solvent
• Attractive bonds form between solute particles and solvent
particles
• “Solvation” or “Hydration” (where water = solvent)
• Releases energy, EXOTHERMIC (- DH)
6
10. What is the per cent by weight of NaCl if 1.75 g
of NaCl is dissolved in 5.85 g of water
• Wt. of solute (NaCl) = 1.75 g
• Wt. of solvent (H2O) = 5.85 g
• ∴ Wt. of solution = 1.75 + 5.85 = 7.60 g
• Hence concentration of NaCl % by weight
• 1.75/ 7.60 X 100 = 23.0
10
11. Parts per Million (ppm) and
Parts per Billion (ppb)
10
9
solutionofmassTotal
solutioninAof
XMass
ppb
10
6
solutionofmassTotal
solutioninAof
XMass
ppm
11
13. • If n represents moles of solute and N number of moles of
solvent,
𝑋𝑠𝑜𝑙𝑢𝑡𝑒 =
𝑛
𝑛 + 𝑁
• Notice that mole fraction of solvent would be
𝑋𝑠𝑜𝑙𝑣𝑒𝑛𝑡 =
𝑁
𝑛 + 𝑁
• Mole fraction is unitless and 𝑋𝑠𝑜𝑙𝑢𝑡𝑒 + 𝑋𝑠𝑜𝑙𝑣𝑒𝑛𝑡 = 1
13
14. Calculate the mole fraction of HCl in a solution of hydrochloric
acid in water, containing 36 per cent HCl by weight
14
15. Molarity (M)
• Because volume is temperature dependent,
molarity can change with temperature.
• Unit = mol/ litre
mol of solute
L of solution
M =
15
16. What is the molarity of a solution prepared by
dissolving 75.5 g of pure KOH in 540 ml of solution.
16
17. What weight of HCl is present in 155 ml of a 0.540 M
solution
17
18. Molality (m)
• Because neither moles nor mass change with
temperature, molality (unlike molarity) is NOT
temperature dependent.
• Unit = mol/ kg
mol of solute
kg of solvent
m =
18
19. What is the molality of a solution prepared by dissolving 5.0 g
of toluene (C7H8) in 225 g of benzene (C6H6) ?
19
20. Normality (N)
• The normality of a solution is the gram equivalent weight
of a solute per litre of solution.
• Normality is the only concentration unit that is reaction
dependent.
solutionofLitre
soluteofweightequivalentGram
Normality
20
21. Equivalent weight (g/Eq)
• It is the mass of one equivalent, that is the mass of a
given substance which will:
• Supply or react with one mole of hydrogen cations H+ in
an acid–base reaction; or
• Supply or react with one mole of electrons e− in a redox
reaction.
• It is that weight of any atom/molecule which displaces
1.008 g of H, 19 g of F or 8 g of O.
/moleequivalent
weightmolecular
weightEquivalent
21
22. 5 g of NaCl is dissolved in 1000 g of water. If the density of the
resulting solution is 0.997 g/ml, calculate the molality,
molarity, normality and mole fraction of the solute,
assuming volume of the solution is equal to that of solvent
22
26. Avogadro Number
• Avogadro hypothesized that there was a specific number
that would represent the number of atoms or molecules in
a mole of that atom or molecule.
• The weight of that unit known as a mole would be
equivalent to the molecular weight of the atom or
molecule in grams. (Mole = Molecular weight in grams)
26
27. • According to this theory, one mole of carbon-12 would have a
mass of 12 grams because carbon-12 has an atomic weight of
12.
• One mole of hydrogen would weigh one gram
• It would contain the same number of atoms as one mole of
carbon.
• The magical number was, in fact, discovered to be 6.023E23
(6.023 X 1023)
27
28. SOLUTIONS OF LIQUID IN
LIQUID
Ideal and Real solutions
Raoult’s Law
Deviation from Raoult’s law
28
29. Solutions of liquid in liquid
Liquid pairs
Completely
miscible
Partially
miscible
Completely
immiscible
Real
solutions
Ideal
solutions
29
31. • No heat is evolved or absorbed during
mixing
• Final volume of sol.= sum of both.
• The properties of solution such as vapour
pressure, surface tension, viscosity etc are
the average of the two pure liquids.
31
33. Ideal mixtures and intermolecular
forces
• In a pure liquid, some of the
more energetic molecules have
enough energy to overcome the
intermolecular attractions and
escape from the surface to form a
vapour.
• The smaller the intermolecular
forces, the more molecules will
be able to escape at any
particular temperature
Liquid A
33
34. • If you have a second liquid, the same thing is true.
• At any particular temperature a certain escaping tendency
Liquid B
34
35. • In an ideal mixture of these two liquids.
• There will be equal evaporation and hence equal vapour
pressure
1:1
Solution of A + B
35
36. Vapour pressure
• Vapour pressure or equilibrium vapour pressure is the pressure of a
vapour in thermodynamic equilibrium with its condensed phases in a
closed system.
3:2
36
37. Raoult’s Law (1887)
• Partial vapour pressure of each volatile constituent is equal to the
vapour pressure of the pure constituent multiplied by its mole
fraction in the solution. Thus, for two constituents A and B,
PA = PA° XA
PB = PB° XB
PA and PB – partial vapour pressure
XA and XB – mole fraction concentration
PA° and PB° - vapour pressure of pure components
• The total vapour pressure of the mixture is equal to the sum of
the individual partial pressures.
Total Vapour Pressure = PA + PB
37
38. • E.g. if vapour pressure of ethylene chloride in the pure
state is 236 mm Hg at 50°C, then in a solution consisting
of a mole fraction of 0.4 ethylene chloride and 0.6
benzene, the partial vapour pressure of ethylene chloride
is 40% of 236 mm.
PA = PA° XA
Pec = Pec° Xec
Pec = 236 X 0.4
Pec = 94.4 mm
38
39. The presence of a non-volatile solute means that fewer solvent
particles are at the solution’s surface, so less solvent evaporates!
Escaping tendency decreases
39
40. • Thus, in an ideal solution, when liquid A is
mixed with liquid B in a manner depending on
the mole fractions of A and B present in the
final solution.
• This will diminish the escaping tendency of
each constituent, leading to a reduction in the
rate of escape of the molecules of A and B from
the surface of liquid.
• The total pressure is the sum of the partial
pressures of all the constituents.
P = PA + PB
40
44. Negative deviation
Cohesion
Adhesion
Vapour pressure of
solution less than expected
These are cases where
the molecules break
away from the mixture
LESS easily than they do
from the pure liquids.
New STRONGER forces
must exist in the mixture
than in the original
liquids.
A↔B 〉〉 A↔A, or B↔B
44
47. • Dilution of chloroform (A) by the addition of acetone (B).
• Addition of B to A tends to reduce the vapour pressure of A to a
greater extent than can be accounted for by the simple dilution.
• Chloroform and acetone manifest such attraction for one
another through the formation of a hydrogen bond further
reducing the escaping tendency of each constituent.
47
48. This pair forms weak compound, Cl3C-H…O=C(CH3)2
which can be isolated and identified.
HC
Cl
Cl
Cl
O C
CH3
CH3
Reaction between dipolar molecules, or between a dipolar
and a non polar molecule, may also lead to negative
deviations.
48
49. Positive deviation
Vapour pressure of
solution greater than
expected
These are cases where the
molecules break away
from the mixture
MORE easily than they do
from the pure liquids. New
WEAKER forces
must exist in the mixture
than in the original liquids.
A↔B << A↔A, or B↔B
Cohesion
Adhesion
49
50. Ethyl alcohol (A)
Chloroform (B)
Solution of chloroform in
ethyl alcohol
Benzene + Ethyl
alcohol
Carbon
disulphide +
Acetone
Other
examples
50
52. • Raoult’s law describes the behavior of either of the
component of a real liquid pair only when that substance
is present in high concentration and thus is considered to
be the solvent.
• In such a situation Raoult’s law can be expressed as
Psolvent = P°solvent Xsolvent
• It is valid only for the solvent of a nonideal solution that
is sufficiently dilute with respect to the solute. It cannot
hold for the component in low concentration, that is, the
solute in a dilute solution.
52
53. Limitations of Raoult’s
law
Real
solutions
In real solutions the concentration of solute is high
and the intermolecular forces between solute-solute
and solute-solvent are high. This causes deviations.
Volatile
solute
It is applicable to only non-volatile solute. As volatile
solutes contribute to the vapour pressure which may
cause deviation.
Solutes
which
associate or
dissociate
If it associates it leads to reduction in lowering of
vapour pressure and if it dissociates then vapour
pressure lowering would be increased.
53
54. Lowering of vapour
pressure
• According to Raoult’s law, the vapour pressure of a
solvent over a dilute solution is equal to the vapour
pressure of pure solvent multiplied by its mole fraction
𝑝 = 𝑝1
𝑜 𝑋1---------------------- 1
• Because the solute is non-volatile, the vapour pressure of
the solvent is identical to the total vapour pressure of the
solution
54
55. • It is more convenient to express vapour pressure of
the solution in terms of the concentration of the
solute rather than the mole fraction of the solvent,
the conversion maybe achieved as follows:
𝑋1 + 𝑋2 = 1
𝑋1 = 1 − 𝑋2-------------------2
• Where, X1 = mole fraction of the solvent
X2 = mole fraction of the solute
• Substituting 2 in 1, we get
p = 𝑝1
𝑜
(1 − 𝑋2)
𝑝0
1 − p = 𝑝1
0 𝑋2
55
56. 𝑝1
𝑜 − 𝑝
𝑝1
𝑜
=
∆𝑝
𝑝 𝑜
1
= 𝑋2 =
𝑛2
𝑛1 + 𝑛2
∆𝑝
𝑝 𝑜
1
=
𝑤2
𝑀2
𝑤2
𝑀2
+
𝑤1
𝑀1
In the above eq.
ΔP = P1° – P is the lowering of the
vapour pressure; and
ΔP / P1° is the relative vapour
pressure lowering.
56
57. • If the concentration of the solute is very less, its
number of moles in the denominator can be
ignored, thus the equation would become:
∆𝑝
𝑝 𝑜
1
=
𝑤2
𝑀2
𝑤1
𝑀1
∆𝑝
𝑝 𝑜
1
=
𝑤2 𝑀1
𝑤1 𝑀2
Vapour pressure lowering can be used to calculate
molecular weight of a compound
57
58. AEROSOLS
• Uses Raoult’s law.
• It has a drug and a propellant.
• Common propellants used:
• Trichloromonofluoromethane (propellant 11)
• Dichlorodifluoromethane (propellant 12)
58
59. Henry’s Law
• The effect of partial pressure on solubility of gases
• At pressure of few atmosphere or less, solubility of gas
solute follows Henry Law which states that the amount of
solute gas dissolved in solution is directly proportional to
the amount of pressure above the solution
c = k P
c = solubility of the gas (M)
k = Henry’s Law Constant
P = partial pressure of gas
59
61. Henry’s Law & Soft Drinks
• Soft drinks contain “carbonated water” –
water with dissolved carbon dioxide gas.
• The drinks are bottled with a CO2 pressure
greater than 1 atm.
• When the bottle is opened, the pressure of
CO2 decreases and the solubility of CO2
also decreases, according to Henry’s Law.
• Therefore, bubbles of CO2 escape from
solution.
61
62. Henry’s law applies to the
SOLUTE and
Raoult’s law applies to the
SOLVENT
in dilute solutions of real liquid
pairs.
62
64. Properties of solutions
• Solutions have properties different from both solute and
solvent
• 4 types of properties
64
Additive Constitutive Colligative
Additive &
Constitutive
65. Additive properties
• Additive Properties: Additive properties are those
properties which is the sum of the corresponding
properties of the atoms constituting the molecule.
• These properties only depend on the types of the atom
and their numbers
• e.g., mass is a additive property, similarly molar volume
is also a good example of additive properties.
65
66. Constitutive properties
• Constitutive property of a molecule is the property which
depends upon the constitution of the molecule
• i.e., upon the arrangements of atoms within the molecule
e.g.,
• Optical activity.
66
67. Additive and constitutive
properties
• The physical property which depend upon the number of
atom in a molecule as well as their constitution
• e.g., atomic volume, parachor etc.
67
68. Colligative properties
• Colligative properties are those properties, which depends
upon the number of molecules present in a substance
• e.g., vapour pressure of gas, elevation in boiling point,
depression of freezing point, osmotic pressure of the
solution, etc.
68
70. Lowering of vapour pressure
• Pressure is measured with a manometer
• When a non volatile solute is combined with a
volatile solvent, the vapour above the solution is
provided by the solvent only.
• Solute reduces the escaping tendency of solvent.
• Vapour pressure of a solution containing a non
volatile solute is lowered proportional to the relative
number of the solute molecules.
• Therefore the vapour pressure of the solvent, P1 is
identical to the total pressure of the solution, P.
70
71. The presence of a non-volatile solute means that fewer solvent
particles are at the solution’s surface, so less solvent evaporates!
Escaping tendency decreases
71
72. • It is more convenient to express the vapour pressure
of the solution in terms of concentration of solute
rather than the mole fraction of solvent
• The sum of the mole fractions of the constituents in
a solution is unity:
X1 + X2 = 1
X1 = 1 – X2
Where,
• X1 is the mole fraction of the solvent; and
• X2 is the mole fraction of the solute.
72
73. Raoult’s eq.
73
In the above eq.
ΔP = P1° – P is the lowering of the
vapour pressure; and
ΔP / P1° is the relative vapour
pressure lowering.
75. Methods for determination
of vapour pressure lowering
Methods
Static
Barometric
method
Manometer
– isopiestic
method
Hill and
Baldes
method
Wescor
method
Dynamic
Ostwald
Walker
75
76. Barometric Method
• Raoult measured the individual
vapour pressure of a liquid and
then the solution by this method.
• He introduced the liquid or the
solution into Toricellian vacuum of
a barometer tube and measured the
depression of the mercury level.
• This method is neither practicable
nor accurate as the lowering of
vapour pressure is too small.
76
77. Manometer
• Vapour pressure lowering is obtained by
subtracting the vapour pressure of the solution
from the vapour pressure of the pure solvent.
77Vapour pressure
of solution
Vapour
pressure
lowering
Vapour pressure
of solvent
78. 78Apparatus for the isopiestic method
The vapour pressure of KCl solution of various
concentrations have been determined accurately
and thus the vapour pressure of the test solution
that is isopiestic is thus readily obtained.
Isopiestic method is used for precise determination of vapour pressures.
80. It consists of combination
of wires of different alloys
formed onto two loops and
connected to a
galvanometer.
Used for determining the
relative vapour pressure of
small amounts of liquids.
This thermoelectric method
measure the change in
potential with respect to
change in vapour pressure.
The solution of known
vapour pressure and an
unknown evapourate in a
chamber maintained at
constant humidity.
Vapour pressure lowering
of solution is then obtained
from a standard curve of
vapour pressure versus
galvanometer readings of
potential.
This method is used to
study the colligative
properties of ophthalmic
solutions.
80
81. Wescor vapour pressure osmometer.
• It is the fastest and easiest method of determining
osmolality.
• Therefore it is the method of choice for most of the fluids
in biology and medicine in which water is the solvent.
• The test solution is absorbed onto a filter paper disk
which is usually 2 to 10 µL.
• The disk is placed in a sealed chamber near the
thermocouple, which is cooled below the dew point of the
solution.
• Thermocouple is then equilibrated to the dew point of the
solution whereupon its potential is recorded.
• The potential determined is proportional to the vapour
pressure lowering.
• Reference standard solutions are used to calibrate the
potential readings against known vapour pressures at the
ambient temperature.
81
83. • This instrument has been applied to quantitating sodium in
isotonic solutions and studying the colligative properties of
parenteral solutions.
• This instrument is also called as vapour pressure
differentiometers as it does not involve membrane diffusion
operation.
83
84. Ostwald and Walker’s Dynamic
Method (Gas Saturation Method)
• In this method the relative lowering of vapour pressure can be determined
straightway.
• The measurement of the individual vapour pressures of a solution and
solvent is thus eliminated.
• Procedure. The apparatus used by Ostwald and Walker is shown in Fig. It
consists of two sets of bulbs :
(a) Set A containing the solution
(b) Set B containing the solvent
• Each set is weighed separately. A slow stream of dry air is then drawn by
suction pump through the two sets of bulbs.
• At the end of the operation, these sets are reweighed.
• From the loss of weight in each of the two sets, the lowering of vapour
pressure is calculated.
• The temperature of the air, the solution and the solvent must be kept
constant throughout.
84
87. • Knowing the loss of mass in set B (w2) and the total loss of
mass in the two sets (w1 + w2), we can find the relative
lowering of vapour pressure from equation (4).
• If water is the solvent used, a set of calcium chloride tubes
(or a set of bulbs containing conc. H2SO4) is attached to the
end of the apparatus to catch the escaping water vapour.
• Thus the gain in mass of the CaCl2-tubes is equal to (w1 +
w2), the total loss of mass in sets A and B.
87
89. • The study of the vapour pressures of mixtures of
completely miscible liquids has proved of great help in
the separation of the liquids by fractional distillation.
• The vapour pressures of two liquids with varying
composition have been determined at constant
temperature.
• By plotting the vapour pressure against composition it
has been revealed that, in general, mixtures of the
miscible liquids are of three types.
89
90. Miscible liquids
1. First Type of Mixtures of Miscible
Liquids (Maximum boiling point
azeotropic solutions)
2. Second Type of Mixtures of
Miscible Liquids (Minimum boiling
point azeotropic solutions)
3. Third Type of Mixtures of Miscible
Liquids
90
92. Azeotrope / Azeotropic Mixture
• Very large deviations from ideality lead to a special class of
mixtures known as azeotropes, azeotropic mixtures, or
constant-boiling mixtures.
• Azeotrope is a special class of liquid mixture that boils at a
constant temperature at a certain composition.
• At this condition, it behaves as if it was one component with
one constant boiling point.
92
93. First Type of Mixtures of Miscible
Liquids (Maximum boiling point
azeotropic solutions)
• For this type of solutions the vapour pressure curve
exhibits a minimum.
• If we take a mixture which has an excess of X (more
volatile component), we are somewhere at C on the
curve.
• When this is distilled the vapour will contain excess of X
and thus the remaining mixture will get richer in Y.
• Finally we reach the point D where vapour pressure is
minimum and thus boiling point is maximum.
• Here the mixture will distil unchanged in composition.
93
96. • It is obvious that complete separation of this type of
solutions into components is impossible.
• At best it can be resolved into one pure component and
the constant boiling mixture.
• Solutions of this type which distil unchanged at a
constant temperature and show a maximum boiling point
are called maximum boiling point azeotropic solutions.
96
97. Maximum boiling
azeotropes
It occurs when the negative deviations are very large
The total pressure curve in this case passes through
a minimum, giving rise to a maximum in
the temperature (i.e. boiling point)
EXAMPLES
Hydrochloric acid - Water (11.1 mole% HCl, 110 oC, 1
atm)
Acetone - Chloroform (65.5 mole% chloroform, 64.5 oC,
1 atm)
Nitric acid – Water (68 mole% HNO3 120 oC, 1 atm)
97
98. Second Type of Mixtures of Miscible
Liquids (Minimum boiling point
azeotropic solutions)
• Ethanol and water mixtures offer a good example of this
type.
• Ethanol-water mixture containing 95.6 per cent ethanol
boils at the minimum temperature 78.13°.
• Thus it is very difficult to obtain pure absolute alcohol by
distillation.
• This difficulty has, however, been overcome by adding
benzene which form a low boiling mixture with water and
on distillation it comes over leaving pure ethanol behind.
98
101. • OTHER EXAMPLES
• Ethanol-Water system which at 1 atm occurs at 89.4
mole percent ethanol and 78.2 oC.
• Carbon disulfide – Acetone 61.0 mole% CS2, 39.25 oC,
1 atm
• Benzene - Water (29.6 mole% H2O, 69.25 oC, 1 atm)
101
102. Third Type of Mixtures of
Miscible Liquids
• In this case the vapour pressures of mixtures always lie between
the vapour pressures of pure components and thus the vapour-
pressure composition curve is a straight line.
• Suppose we have a mixture containing excess of Y which is
represented by point G on the curve.
• On distillation X component being more volatile will be obtained
in greater proportion in the distillate and we gradually travel along
the curve AB.
• The latter fractions will, of course, be poorer in X and richer in Y
till we reach the 100 per cent Y-axis, when all the X will have
passed over.
102
103. • Only in this type of solutions we can completely separate
the components by fractional distillation.
• Thus methyl alcohol-water mixtures can be resolved into
pure components by distillation.
• Liquid mixtures which distil with a change in
composition are called zeotropic mixtures
103
104. Distillation
Distillation is a widely used method for separating
mixtures based on differences in the conditions required
to change the phase of components of the mixture.
To separate a mixture of liquids, the liquid can be heated
to force components, which have different boiling points,
into the gas phase.
The gas is then condensed back into liquid form and
collected.
Vapourization of a liquid and subsequent condensation
of the resultant gas back to liquid form – Distillation
104
107. Boiling point
The boiling point of an element or a substance is the
temperature at which the vapour pressure of the liquid equals
the environmental pressure surrounding the liquid (760 mm
Hg)
Atmospheric
pressure
Vapour
pressure
Boiling
point
107
110. USING BP TO SEPARATE A
MIXTURE OF 2 LIQUIDS
110
111. Miscible liquids – fractional
distillation (Theory)
• To understand the process of fractional distillation we must
have an idea of the composition of the vapour phase and that
of the liquid mixtures at different boiling temperatures.
• Thus for this purpose it is not the vapour-pressure composition
curve but rather the temperature-composition curve that is
important.
• If we plot the boiling point of liquid mixture against its
composition and the composition of the vapour in contact with
it, we get two separate curves for each type of solutions.
• The curves obtained for the third type are shown
111
113. The curves AEB and ADB
are the temperature
composition curves for the
vapour and liquid
respectively.
At any boiling temperature
C the composition of liquid
mixture is represented by J
and that of the vapour in
equilibrium by K.
Obviously, the more volatile
component Y is present in
greater proportion in the
vapour than the liquid
mixture.
Thus the condensed vapour
or the distillate will be
richer in Y.
If the distillate so obtained
be now subjected to
distillation, it will boil at F
and the fresh distillate will
have the composition L
corresponding to I.
Thus the proportion of Y in
the second distillate is
greater than in the first one.
In this way by repeating the
process of fractional
distillation it is obvious that
we can get almost pure Y.
113
115. • In first type of solutions if we have a boiling mixture
represented by Y its vapour will be poor in Y than the liquid
mixture and the boiling point would gradually rise till we reach
the maximum point C where the composition of liquid and
vapour is the same.
• Here the distillation proceeds without change of composition.
• Similarly in the second type, if we have a boiling mixture
represented by the point X', the amount of Y in vapour is higher
and gradually the boiling point falls to the minimum C' where
the vapour and the liquid mixtures have the same composition.
• At this temperature the mixture boils without any change in
composition.
• Thus it is proved that the second and first type of solutions
are not capable of being separated by fractional
distillation. 115
116. Apparatus for fractional
distillation
• The efficiency of the process of fractional distillation is considerably
enhanced by the use of the so-called Fractionating Columns.
• These are of different designs.
• An effective and simple fractionating column usually employed for
laboratory use consists of a long glass tube packed with glass beads or
specially made porcelain rings.
• The glass tube blown into bulbs at intervals may also constitute a
fractionating column.
• For industrial purposes a fractionating tower is employed.
• A fractionating tower is divided into several compartments by means of
tray that are set one above the other.
• There is a hole in the centre of every tray which is covered by bubble cap.
• Each tray has an overflow pipe that joins it with the tray below by
allowing the condensed liquid to flow down
116
118. The fractionating column or
tower is fitted in the neck of the
distillation flask or the still so
that the vapours of the liquid
being heated pass up through it.
The temperature falls in the
column as vapours pass from
bottom to the top.
The hot vapours that enter the
column get condensed first in
the lowest part of it.
As heating is continued more
vapours ascend the column and
boil the liquid already
condensed, giving a vapour
which condenses higher up in
the column.
This liquid is heated in turn by
more vapours ascending the
column.
Thus the liquid condensed in
the lowest part is distilled on to
the upper part.
In this manner a sort of
distillation and condensation
goes on along the height of the
column which results in the
increase of the proportion of the
volatile component in the
outgoing vapours.
At every point in the column
there exists an equilibrium
between liquid and vapour.
This is established quickly by
and upward flow of vapours
and the downward flow of
liquid, a large surface area and
a slow rate of distillation.
118
119. • A simple
distillation of
a mixture of
methanol and
water and the
liquid vapour
equilibrium
states are
depicted
119
120. • It is clear that the liquid-vapour equilibria change
regularly in moving up the column.
• We may withdraw mixtures of varied compositions from
different points on the column.
• This is done in the fractional distillation of crude oil in a
refinery where different products of industrial use are
conveniently separated.
120
121. Immiscible liquids
• When 2 immiscible liquids are heated while being agitated,
each constituent independently exerts its own vapour pressure
as a function of temperature as the other liquid does not exist
• Boiling begins when the sum of the partial pressures of the two
liquids just exceeds the atmospheric pressure
• This principle is used in steam distillation
121
122. Steam Distillation
• Organic substances insoluble in
water can purified
• Water insoluble substances can
separated at temperature below
their degradation temperature
Water
1oo ◦C
Bromo-benzene
156.2 ◦C
Mixture
95 ◦C
Useful for separating volatile oils from plant tissue without
decomposing the oils
122
124. Steam distillation
• Distillation carried in a current of steam is called steam
distillation.
• This technique is widely used for purification of organic
liquids which are steam volatile and immiscible with water
(e.g., aniline).
• The impure organic liquid admixed with water containing non-
volatile impurities is heated and steam passed into it.
• The vapour of the organic liquid and steam rising from the
boiling mixture pass into the condenser.
• The distillate collected in the receiver consists of two layers,
one of the pure organic liquid and the other of water.
• The pure liquid layer is removed by means of a separator
funnel and further purified.
124
125. Theory of steam
distillation
• The vapour pressure of a liquid rises with increase of
temperature.
• When the vapour pressure equals the atmospheric pressure, the
temperature recorded is the boiling point of the given liquid.
• In case of a mixture of two immiscible liquids, each
component exerts its own vapour pressure as if it were alone.
• The total vapour pressure over the mixture (P) is equal to the
sum of the individual vapour pressures (p1, p2) at that
temperature.
• P = p1 + p2
125
126. • Hence the mixture will boil at a temperature when the
combined vapour pressure P, equals the atmospheric
pressure.
• Since P > p1 or p2, the boiling point of the mixture of
two liquids will be lower than either of the pure
components.
126
127. • In steam distillation the organic liquid is mixed with water
(bp 100°C).
• Therefore the organic liquid will boil at a temperature lower
than 100°C.
• For example, phenylamine (aniline) boils at 184°C but the
steam distillation temperature of aniline is 98°C.
• Steam distillation is particularly used for the purification
of an organic liquid (such as phenylamine) which
decomposes at the boiling point and ordinary distillation
is not possible.
127
129. • Normal boiling point is the temperature at
which the vapour pressure of the liquid
becomes equal to an external pressure of 760
mm Hg.
• A solution will boil at higher temperature than
the pure solvent.
• The more the solute will be dissolved the
greater will be the boiling point elevation.
• The boiling point of a solution of a non volatile
solute is higher than that of the pure solvent
because the solute lowers the vapour pressure
of the solvent.
129
131. Relationship between Elevation of
Boiling Point and Lowering of Vapour-
pressure
• When a liquid is heated, its vapour pressure rises and when it
equals the atmospheric pressure, the liquid boils.
• The addition of a non volatile solute lowers the vapour
pressure and consequently elevates the boiling point as the
solution has to be heated to a higher temperature to make its
vapour pressure become equal to atmospheric pressure.
• If Tb is the boiling point of the solvent and T is the boiling
point of the solution, the difference in the boiling points (ΔT)
is called the elevation of boiling point.
• T – Tb = ΔT
131
132. • Consider the vapour pressure curves of
the pure solvent, and solutions (1) and
(2) with different concentrations of
solute
• For dilute solutions, the curves BD and
CE are parallel and straight lines
approximately.
• Therefore for similar triangles ACE
and ABD, we have
• where p – p1 and p – p2 are lowering
of vapour pressure for solution 1 and
solution 2 respectively.
• Hence the elevation of boiling point
is directly proportional to the
lowering of vapour pressure
• ΔT ∝ p – ps/p 132
Ostwald-Walker method of
measuring the relative lowering of
vapour pressure
134. • where Kb is a constant called Boiling point constant or
Ebulioscopic constant of molal elevation constant.
• If w/m = 1, W = 1, Kb = ΔT.
• Thus, Molal elevation constant may be defined as the
boiling-point elevation produced when 1 mole of solute is
dissolved in one kg (1000 g) of the solvent.
• If the mass of the solvent (W) is given in grams, it has to be
converted into kilograms.
• Thus the expression (5) assumes the form
• where ΔT = elevation of boiling point;
• Kb = molal elevation constant;
• w = mass of solute in grams;
• m = mol mass of solute; and
• W = mass of solvent in grams.
• The units of Kb are °C kg/ mol
134
135. • Kb has a characteristic value for each solvent.
• It may considered as the boiling point elevation for an
ideal 1m solution.
• Kb is the ratio of the boiling point elevation to the molal
concentration in an extremely dilute solution in which
the system is approximately ideal.
135
137. • After applying Clapeyron equation it is written as
137
Where,
• Vv and V1 are the molar volume of the gas and
the molar volume of the liquid,
• Tb is the boiling point of the solvent, and
• Δ Hv is the molar heat of vapourization.
Vv the volume of 1 mole of gas is replaced by RTb/P°
V1 is negligible compared to Vv the equation becomes
OR
138. but Δp/ P1° = X2 and this equation can be written as
138
where R = gas constant; Tb = boiling point of solvent; Hv = molar latent heat of
vaporization
Thus for water R = 8.134 J/mol; T = 373 K, Hv = 2260 J/g
140. Landsberger-Walker
Method
• This method was introduced by Landsberger and modified by
Walker.
• Apparatus. The apparatus used in this method is shown and
consists of :
• (i) An inner tube with a hole in its side and graduated in ml;
• (ii) A boiling flask which sends solvent vapour in to the graduated
tube through a ‘rosehead’ (a bulb with several holes)’
• (iii) An outer tube which receives hot solvent vapour issuing from
the side-hole of the inner tube;
• (iv) A thermometer reading to 0.01 K, dipping in solvent or
solution in the inner tube.
140
141. 141
• Pure solvent is placed in the graduated
tube and vapour of the same solvent
boiling in a separate flask is passed into it.
• The vapour causes the solvent in the tube
to boil by its latent heat of condensation.
• When the solvent starts boiling and
temperature becomes constant, its boiling
point is recorded.
• Now the supply of vapour is temporarily cut
off and a weighed pellet of the solute is
dropped into the solvent in the inner tube.
• The solvent vapour is again passed
through until the boiling point of the solution
is reached and this is recorded.
• The solvent vapour is then cut off,
thermometer and rosehead raised out of
the solution, and the volume of the solution
read.
143. • From a difference in the boiling points of solvent and
solution, we can find the molecular weight of the solute
by using the expression
• where w = weight of solute taken, W = weight of solvent
which is given by the volume of solvent (or solution)
measured in ml multiplied by the density of the solvent at
its boiling point.
143
144. Disadvantage
• Superheating:- The heating of the vapours of a solvent
which increases its temperature from its boiling point is
called superheating
• Complicated
144
145. Cottrell’s Method
• A method better than Landsberger-Walker method was
devised by Cottrell (1910).
• Apparatus. It consists of :
• (i) a graduated boiling tube containing solvent or solution;
• (ii) a reflux condenser which returns the vapourised solvent
to the boiling tube;
• (iii) a thermometer reading to 0.01 K, enclosed in a glass
hood;
• (iv) A small inverted funnel with a narrow stem which
branches into three jets projecting at the thermometer bulb.
145
146. Beckmann thermometer
• It is differential thermometer.
• It is designed to measure small changes in
temperature and not the temperature itself.
• It has a large bulb at the bottom of a fine
capillary tube.
• The scale is calibrated from 0 to 6 K and
subdivided into 0.01 K.
• The unique feature of this thermometer, however,
is the small reservoir of mercury at the top.
• The amount of mercury in this reservoir can be
decreased or increased by tapping the
thermometer gently.
• In this way the thermometer is adjusted so that
the level of mercury thread will rest at any
desired point on the scale when the instrument is
placed in the boiling (or freezing) solvent.
146
147. • Procedure. The apparatus is fitted up as shown
• Solvent is placed in the boiling tube with a porcelain piece lying
in it.
• It is heated on a small flame (micro burner).
• As the solution starts boiling, solvent vapour arising from the
porcelain piece pump the boiling liquid into the narrow stem.
• Thus a mixture of solvent vapour and boiling liquid is
continuously sprayed around the thermometer bulb.
• The temperature soon becomes constant and the boiling point of
the pure solvent is recorded.
• Now a weighed pellet of the solute is added to the solvent and
the boiling point of the solution noted as the temperature
becomes steady.
• Also, the volume of the solution in the boiling tube is noted.
• The difference of the boiling temperatures of the solvent and
solution gives the elevation of boiling point.
• While calculating the molecular weight of solute the volume of
solution is converted into mass by multiplying with density of
solvent at its boiling point
147
149. • Freezing point/ melting point – temperature at which solid and
liquid phases are in equilibrium under a pressure of 1 atm.
149
150. • When solute is added, FP < Normal FP
• FP is depressed when solute inhibits solvent from
crystallizing.
150
When solution freezes the solid form is almost always pure.
Solute particles does not fit into the crystal lattice of the
solvent because of the differences in size.
The solute essentially remains in solution and blocks other
solvent from fitting into the crystal lattice during the freezing
process.
151. • A situation exists similar to elevation of boiling point.
• Freezing point depression is proportional to molal concentration of
the solute
Δ Tf = Kfm
Where, Δ Tf – freezing point depression
Kf – molal depression constant or cryoscopic constant
151
152. Relation between Depression of Freezing-
point and Lowering of Vapour-pressure
• The vapour pressure of a pure liquid changes with temperature as shown
by the curve ABC,
• There is a sharp break at B where, in fact, the freezing-point curve
commences.
• Thus the point B corresponds to the freezing point of pure solvent, Tf.
• The vapour pressure curve of a solution (solution 1) of a non-volatile
solute in the same solvent is also shown.
• It is similar to the vapour pressure curve of the pure solvent and meets
the freezing point curve at F, indicating that T1 is the freezing point of
the solution.
• The difference of the freezing point of the pure solvent and the solution
is referred to as the Depression of freezing point.
• It is represented by the symbol ΔT or ΔTf .
• Tf – T1 = Δ T
152
153. • When more of the solute is added to the solution 1,
we get a more concentrated solution (solution 2.)
• The vapour pressure of solution 2 meets the
freezing-point at C, indicating a further lowering
of freezing point to T2.
• For dilute solutions FD and CE are approximately
parallel straight lines and BC is also a straight line.
• Since the triangles BDF and BEC are similar,
• where p1 and p2 are vapour pressure of solution 1
and solution 2 respectively.
• Hence depression of freezing point is directly
proportional to the lowering of vapour
pressure.
• ΔT ∝ p – ps/p
153
155. • The value of Kf can be determined by measurement of ΔT by
taking a solute of known molecular mass (m) and substituting
the values in expression (6). The constant Kf , which is
characteristic of a particular solvent, can also be calculated from
the relation
• where Tf = freezing point of solvent in K; Lf = molar latent heat
of fusion; R = gas constant.
• Hence for water, Tf = 273 K and Lf = 336 J g–1. Therefore,
155
157. Beckmann’s Method (1903)
• Apparatus: It consists of
• (i) A freezing tube with a side-
arm to contain the solvent or
solution, while the solute can
be introduced through the
side-arm;
• (ii) An outer larger tube into
which is fixed the freezing
tube, the space in between
providing an air jacket which
ensures a slower and more
uniform rate of cooling;
• (iii) A large jar containing a
freezing mixture e.g., ice and
salt, and having a stirrer.
157
158. • Procedure. 15 to 20 g of the solvent is taken in the freezing point of
the solvent by directly cooling the freezing point tube and the
apparatus is set up as shown so that the bulb of the thermometer is
completely immersed in the solvent.
• First determine the approximate freezing point of the solvent by
directly cooling the freezing point tube in the cooling bath.
• When this has been done, melt the solvent and place the freezing-
point tube again in the freezing bath and allow the temperature to
fall.
• When it has come down to within about a degree of the approximate
freezing point determined above, dry the tube and place it cautiously
in the air jacket.
• Let the temperature fall slowly and when it has come down again to
about 0.5° below the freezing point, stir vigorously.
• This will cause the solid to separate and the temperature will rise
owing to the latent heat set free.
• Note the highest temperature reached and repeat the process to get
concordant value of freezing point.
158
159. • The freezing point of the solvent having been accurately
determined, the solvent is remelted by removing the tube
from the bath, and a weighed amount (0.1–0.2 g) of the
solute is introduced through the side tube.
• Now the freezing point of the solution is determined in
the same way as that of the solvent.
• Knowing the depression of the freezing point, the
molecular weight of the solute can be determined by
using the expression
159
160. • This method gives accurate results, if the following
precautions are observed :
(a) The supercooling should not exceed 0.5°C.
(b) The stirring should be uniform at the rate of about one
movement per second.
(c) The temperature of the cooling bath should not be 4° to
5° below the freezing point of the liquid
160
161. Rast’s Camphor Method
• This method due to Rast (1922) is used for determination
of molecular weights of solutes which are soluble in
molten camphor.
• The freezing point depressions are so large that an
ordinary thermometer can be used
161
162. • Pure camphor is powdered and introduced into a capillary tube which is
sealed at the upper end.
• This is tied along a thermometer and heated in a glycerol bath.
• The melting point of camphor is recorded.
• Then a weighed amount of solute and camphor (about 10 times as much)
are melted in test-tube with the open end sealed.
• The solution of solute in camphor is cooled in air.
• After solidification, the mixture is powdered and introduced into a
capillary tube which is sealed.
• Its melting point is recorded as before.
• The difference of the melting point of pure camphor and the mixture,
gives the depression of freezing point.
• In modern practice, electrical heating apparatus is used for a quick
determination of melting points of camphor as also the mixture.
• The molal depression constant of pure camphor is 40°C.
• But since the laboratory camphor may not be very pure, it is necessary to
find the depression constant for the particular sample of camphor used by
a preliminary experiment with a solute of known molecular weight.
162
165. Applications
• Salting of snow
• Antifreeze used in car batteries –
Propylene glycol, glycerol, honey etc
165
Elevation of boiling point and
depression of freezing point can help
in determining molecular weights of
substances
167. • Diffusion – both the solute and solvent molecules travel freely
• Osmosis – only solvent molecules pass through the semi permeable
membrane.
• Passage of solvent molecules through a semipermeable membrane, from an
area of low solute concentration to an area of high solute concentration is
called as osmosis.
167
168. • This happens by equalization of escaping tendency
of the solvent on both the sides of the membrane.
• Escaping tendency can be measured as osmotic
pressure.
168
169. Osmotic Pressure - The Pressure that must be applied
to stop osmosis
169
170. Preparation
• Addition of non-volatile solute to solvent
• Lowering of vapour pressure
Setup
• Pure solvent is placed adjacent to above solution but separated
by semipermeable membrane
• Solvent molecule pass through membrane into the solution to
dilute out the solute and to raise the vapour pressure back to
original value
Measurement
• Osmotic pressure is measured by:
• Measuring the hydrostatic head appearing in the solution
• Applying a known pressure which just balances the osmotic
pressure
170
171. Osmotic pressure: A lowering of vapour pressure
• Works on the principle of thistle tube
apparatus
• Once equilibrium is obtained, height on
the solution side of the membrane is
greater than the height on the solvent
side
П = hρg
П – osmotic pressure
h – difference in heights
ρ – solution density
g – acceleration due to gravity
171
173. • Two methods:
• Measuring the hydrostatic head appearing in the solution
– NOT USED
• Applying a known pressure which just balances the
osmotic pressure i.e. there is no passage of solvent
molecules through the semipermeable membrane
• Pressure can be measured by a manometer or by more
sensitive electric techniques
173
174. van’t Hoff equation
• 1886 – Jacobus van’t Hoff recognised a relationship
between osmotic pressure, concentration and temperature
• He concluded that,
174
op in a dilute
solution
pressure that the solute
would exert if it were a
gas occupying the same
volume
175. • Where,
• П – osmotic pressure in atm
• V – volume of solution in liters
• n – number of moles of solute
• R – gas constant
• T – absolute temperature
175
ПV = nRT
V
nRT
Where,
c = concentration of solute in
moles/ liter (molarity)
176. Morse equation
• He proved that if concentration when expressed in terms
of molality rather molarity, the experimental results were
more accurate.
П = RTm
176
177. A cell placed in an
isotonic solution. The
net movement of water
in and out of the cell is
zero because the
concentration of
solutes inside and
outside the cell is the
same.
177
178. • If the solute concentration
outside the cell is greater
than that inside the cell,
the solution is hypertonic.
• Water will flow out of the
cell, and crenation results.
178
Cells
shrink
179. • If the solute concentration
outside the cell is less than
that inside the cell, the
solution is hypotonic.
• Water will flow into the
cell, and hemolysis results.
179
Cells
burst
182. • Osmotic pressure can be used in determination of the
molecular weight of substances
182
183. Choice of colligative property
for determination of molecular
weight
Boiling point
elevation
• Solute is non-
volatile
• Doesn’t
decompose at
bp
Freezing point
depression
• Solute should
be volatile
• High accuracy
for solutions
of small
molecules
Osmotic
pressure
• No difficulties
• Widely used
for molecular
weight
determination
of polymers
183