This document discusses various topics related to aqueous solutions and reactions. It begins by defining key terms like solute, solvent, electrolyte and providing examples. It then covers properties of aqueous solutions such as conductivity. Various acid-base reactions and concepts are explained like Brønsted-Lowry acids and bases, neutralization reactions. Oxidation-reduction reactions and oxidation numbers are also discussed. Finally, the document covers concentration of solutions and calculations involving molarity, dilution and preparation of solutions.
An oxidation-reduction (redox) reaction is a type of chemical reaction that involves a transfer of electrons between two species. An oxidation-reduction reaction is any chemical reaction in which the oxidation number of a molecule, atom, or ion changes by gaining or losing an electron.
An oxidation-reduction (redox) reaction is a type of chemical reaction that involves a transfer of electrons between two species. An oxidation-reduction reaction is any chemical reaction in which the oxidation number of a molecule, atom, or ion changes by gaining or losing an electron.
Revision Slides for AQA A-Level Chemistry on the Group Two Elements. Designed for the new Exam Series of June 2017, but relevant for all series and exam boards.
Acids are divided into two categories based on the ease with which they can donate protons to the solvent: i) strong acids and ii) weak acids
Strong acids are acids that completely dissociate in water. The reaction of an acid with its solvent (typically H2O) is called an acid dissociation reaction.
Weak acids are acids that dissociate partially in water. The extent of dissociation is given by the equilibrium constant.
Note:
A measure of the relative strength of an acid is: i) the equilibrium constant ka of the dissociation reaction of the acid in water (depends on temperature) ii) the degree of dissociation α of the acid in water (depends on the concentration of the acid an on temperature).
Revision Slides for AQA A-Level Chemistry on the Group Two Elements. Designed for the new Exam Series of June 2017, but relevant for all series and exam boards.
Acids are divided into two categories based on the ease with which they can donate protons to the solvent: i) strong acids and ii) weak acids
Strong acids are acids that completely dissociate in water. The reaction of an acid with its solvent (typically H2O) is called an acid dissociation reaction.
Weak acids are acids that dissociate partially in water. The extent of dissociation is given by the equilibrium constant.
Note:
A measure of the relative strength of an acid is: i) the equilibrium constant ka of the dissociation reaction of the acid in water (depends on temperature) ii) the degree of dissociation α of the acid in water (depends on the concentration of the acid an on temperature).
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
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.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
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.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
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.
1. Reactions in Aqueous Solution
Chapter 4
Dr. Sa’ib Khouri
AUM- JORDAN Chemistry
By Raymond Chang
2. 2
A solution is a homogenous mixture of two or more
substances.
The solute is the substance present in a smaller
amount. (In a solution may be more than one solute)
The solvent is the substance present in a larger
amount.
Solution Solvent Solute
Soft drink (l)
Air (g)
Soft Solder (s)
H2O
N2
Pb
Sugar, CO2
O2, Ar, CH4
Sn
Aqueous solutions:
the solute is a liquid
or a solid and the
solvent is water
General Properties of Aqueous Solutions
A solution may be gaseous (air), solid
(alloy), or liquid (seawater).
3. 3
An electrolyte is a substance that, when dissolved in
water, results in a solution that can conduct electricity.
A nonelectrolyte does not conduct electricity when
dissolved in water.
nonelectrolyte weak electrolyte strong electrolyte
Electrolytic Properties
4. 4
Examples of strong electrolytes, weak electrolytes, and nonelectrolytes.
Cations (+) and Anions (-) are responsible to conduct electricity in
solution.
Strong Electrolyte – 100% dissociation
NaCl (s) Na
+
(aq) + Cl
-
(aq)
H2O
5. 5
Hydration is the process in which an ion is surrounded by
water molecules arranged in a specific manner.
d+
d-
H2O
Hydration helps to stabilize ions in solution and prevents cations
from combining with anions
The Na
+
and Cl
-
ions are separated from each other and
undergo hydration
7. 7
Precipitation Reactions
Precipitate – insoluble solid that separates from solution
molecular equation
ionic equation
net ionic equation
Pb
2+
+ 2NO3
-
+ 2K
+
+ 2I
-
PbI2 (s) + 2K
+
+ 2NO3
-
K
+
and NO3
-
are spectator ions
Pb(NO3)2 (aq) + 2KI (aq) PbI2 (s) + 2KNO3 (aq)
Pb
2+
+ 2I
-
PbI2 (s)
e.g. Mixing of Pb(NO3)2 and KI solutions forms an insoluble
yellow product, PbI2 through a double-displacement
reaction:
9. 9
Solubility is the maximum amount of solute that will dissolve
in a given quantity of solvent at a specific temperature.
10. 10
Examples of Insoluble Compounds
CdS PbS Ni(OH)2 Al(OH)3
Practice Exercise Classify the following ionic compounds as
soluble or insoluble:
(a) CuS, (b) Ca(OH)2, (c) Zn(NO3)2, (d) Ag2SO4, (e) Na3PO4
11. 11
Writing Net Ionic Equations
1. Write the balanced molecular equation.
2. Write the ionic equation showing the strong electrolytes
completely dissociated into cations and anions.
3. Cancel the spectator ions on both sides of the ionic equation
4. Check that charges and number of atoms are balanced in the
net ionic equation
AgNO3 (aq) + NaCl (aq) AgCl (s) + NaNO3 (aq)
Ag+ + NO3
- + Na+ + Cl- AgCl (s) + Na+ + NO3
-
Ag+ + Cl- AgCl (s)
e.g. Write the net ionic equation for the reaction between
silver nitrate and sodium chloride.
12.
13. Write balance complete molecular equation, ionic equation, and
net ionic equations for the reaction that occurs when Pb(NO3)2
and Na2S solutions are mixed. Identify the spectator ions in the
reaction.
e.g.
Molecular equation
Ionic equation
Net ionic equation
14. General Properties of Acids and Bases
Acids
-Acids have a sour taste; e.g. Vinegar owes its
sourness to acetic acid, citrus fruits contain citric acid
-Acids cause color changes in
plant dyes
-Acids react with certain metals to produce
hydrogen gas
2HCl (aq) + Mg (s) MgCl2 (aq) + H2 (g)
Acid-Base Reactions
15. -Acids react with carbonates and bicarbonates to produce
carbon dioxide gas
2HCl (aq) + CaCO3 (s) CaCl2 (aq) + CO2 (g) + H2O (l)
HCl (aq) + NaHCO3 (s) NaCl (aq) + CO2 (g) + H2O (l)
-Aqueous acid solutions conduct electricity
Bases
-Have a bitter taste
-Feel slippery, e.g.: soaps
-Cause color changes in plant dyes
-Aqueous base solutions conduct electricity
16. 16
Arrhenius acid is a substance that produces H+ (H3O+) in water
Arrhenius base is a substance that produces OH- in water
Bronsted Acids and Bases
Arrhenius’s definitions of acids and bases apply only to
aqueous solutions
17. 17
A Brønsted acid is a proton donor
A Brønsted base is a proton acceptor
Johannes Brønsted (Danish chemist) proposed broader
definitions:
Note: Brønsted’s definition do not require acids and bases to be
in aqueous solution
NH3 (g) + HCl (g) → NH4Cl (s)
Here
HCl (g) is a Brønsted acid
NH3 (g) is a Brønsted base
18. 18
Hydrochloric acid is a Brønsted acid because it donates a
proton in water:
HCl (aq) → H
+
(aq) + Cl
-
(aq)
H+
ion is a hydrogen atom that has lost its electron; that is, it is just a bare
proton and exists in the hydrated form:
The hydrated proton, H3O
+
, is called the hydronium ion
19. 19
Monoprotic acids: yields one hydrogen ion upon ionization
HCl H+ + Cl-
HNO3 H+ + NO3
-
CH3COOH H+ + CH3COO-
Strong acid
Strong acid
Weak acid
Diprotic acids: gives up two H+
ions, in two separate steps
H2SO4 H+ + HSO4
-
HSO4
- H+ + SO4
2-
Strong acid
Weak acid
Triprotic acids: yields three H
+
ions, in three separate steps
H3PO4 H+ + H2PO4
-
H2PO4
- H+ + HPO4
2-
HPO4
2- H+ + PO4
3-
Weak acid
Weak acid
Weak acid
22. 22
Acid-Base Neutralization
acid + base salt + water
HCl (aq) + NaOH (aq) NaCl (aq) + H2O
H+ + Cl
-
+ Na+
+ OH- Na
+
+ Cl
-
+ H2O
H
+
+ OH
-
H2O
A neutralization reaction is a reaction between an acid and a base.
Generally, aqueous acid-base reactions produce water and a salt.
Acid-base reactions generally go to completion.
23. 23
Neutralization reaction involving a weak electrolyte
weak acid + base salt + water
HCN (aq) + NaOH (aq) NaCN (aq) + H2O
HCN + Na
+
+ OH
-
Na
+
+ CN
-
+ H2O
HCN (aq) + OH
-
(aq) CN
-
(aq) + H2O
24. 24
Acid-Base Reactions Leading to Gas Formation
acid + base salt + water + CO2
2HCl (aq) + Na2CO3 (aq) 2NaCl (aq) + H2O +CO2
2H
+
+ 2Cl
-
+ 2Na
+
+ CO3
2- 2Na
+
+ 2Cl
-
+ H2O + CO2
2H+ (aq) + CO3
2- (aq) H2O + CO2
H.W. Write molecular, ionic, and net ionic equations for each of
the following acid-base reactions:
(a) hydrobromic acid (aq) + barium hydroxide (aq) →
(b) sulfuric acid (aq) + potassium hydroxide (aq) →
26. 26
Zn (s) + CuSO4 (aq) ZnSO4 (aq) + Cu (s)
(Zn is oxidized)Zn Zn2+ + 2e-
(Cu2+ is reduced)Cu2+ + 2e- Cu
Zn is the reducing agent
Cu2+ is the oxidizing agent
e.g. Copper wire reacts with silver nitrate to form silver metal.
What is the oxidizing agent in the reaction?
Cu (s) + 2AgNO3 (aq) Cu(NO3)2 (aq) + 2Ag (s)
Cu Cu2+ + 2e- Ag+ + 1e- Ag
(Ag+ is reduced) Ag+ is the oxidizing agent
e.g. When metallic zinc is added to a solution containing
copper(II) sulfate (CuSO4),
28. 28
Oxidation number
1. Free elements (uncombined state) have an oxidation
number of zero.
Na, Be, K, H2, O2, P4 = 0
2. In monatomic ions (composed of only one atom), the
oxidation number is equal to the charge on the ion.
Li+ = +1; Fe3+ = +3; O2- = -2
3. The oxidation number of oxygen is usually –2.
In H2O2 and O2
2- it is –1.
4.4
The number of charges the atom would have in a molecule (or
an ionic compound) if electrons were transferred completely.
29. 29
4. The oxidation number of hydrogen is +1 except when
it is bonded to metals in binary compounds. In these
cases (e.g. NaH), its oxidation number is –1.
6. The sum of the oxidation numbers of all the atoms in a
molecule or ion is equal to the charge on the
molecule or ion.
5. Group IA metals are +1, IIA metals are +2
HCO3
-
O = - 2
H = +1
For C: 3(- 2) + 1 + x = -1
x=+4 C = +4
e.g.
What are the oxidation numbers of all the elements in HCO3
- ?
7. Oxidation numbers do not have to be integers.
e.g. Oxidation number of oxygen in the superoxide ion,
O2
-, is –½.
31. 31
NaIO3
Na = +1 O = -2
3(-2) + 1 + x = 0
x=+5, I = +5
IF7 F = -1
7(-1) + x = 0
x=+7, I = +7
K2Cr2O7
O = -2 K = +1
7(-2) + 2(+1) + 2x = 0
x=+6, Cr = +6
e.g. What are the oxidation numbers of all the elements in each
of these compounds?
NaIO3 IF7 K2Cr2O7
32. 32
Types of Redox Reactions
Combination Reactions
Decomposition Reactions
A combination reaction is a reaction in which two or more
substances combine to form a single product.
Decomposition reactions are the opposite of combination
reactions, or the breakdown of a compound into two or
more components.
33. 3
3
Combustion Reactions
A combustion reaction is a reaction in which a substance reacts with oxygen,
usually with the release of heat and light to produce a flame
Example: Burning of propane (C3H8), a component of natural gas that is used for
domestic heating and cooking:
Here, we focus only on the oxidation number of O atoms, which changes from 0 to -2.
Displacement Reactions
In a displacement reaction, an ion (or atom) in a compound is
replaced by an ion (or atom) of another element.
1. Hydrogen Displacement
All alkali metals and some alkaline earth metals (Ca, Sr, and Ba), which are
the most reactive of the metallic elements, will displace hydrogen from cold
water
34. Zinc (Zn) and magnesium (Mg) do not react with cold water but do react with
hydrochloric acid, as follows:
2. Metal Displacement
A metal in a compound can be displaced by another metal in the elemental state
Example: zinc replacing copper ions and copper replacing silver ions
3.Halogen Displacement.
Another activity series summarizes the halogens’ behavior in halogen
displacement reactions:
F2 >Cl2 > Br2 > I2
35. 35
The metals are arranged according to their ability to displace
hydrogen from an acid or water
The activity series for metals
According to this series, any
metal above hydrogen will
displace it from water or from
an acid, but metals below
hydrogen will not react with
either water or an acid
Any metal listed in the series
will react with any metal (in a
compound) below it. For
example, Zn is above Cu, so
zinc metal will displace copper
ions from copper sulfate.
36. 36
Disproportionation Reaction
an element in one oxidation state is simultaneously oxidized
and reduced.
Here the oxidation number of oxygen in the reactant (-1) both
increases to zero in O2 and decreases to -2 in H2O
This reaction describes the formation of household bleaching
agents
One reactant in a disproportionation reaction always contains an
element that can have at least three oxidation states. The
element itself is in an intermediate.
39. 39
Concentration of solutions
The concentration of a solution is the amount of solute
present in a given quantity of solvent or solution.
Molarity (M) =
moles of solute (n)
liters of solution(V)
e.g. What mass of KI is required to make 500 mL of
a 2.80 M (mol/L) KI solution?
volume of KI solution (L) moles KI grams KI
500. mL = 232 g KI
166 g KI
1 mol KI
x
2.80 mol KI
1 L soln
x
1 L
1000 mL
x
Or directly: mass = V (L) X M (mol/L) X MM (g/mol)
40. 40
Preparing a solution of known molarity
(a) known amount of a solid solute is transferred into the volumetric flask; then water
is added through a funnel.
(b) The solid is slowly dissolved by gently swirling the flask.
(c) After the solid has completely dissolved, more water is added to bring the
level of solution to the mark. Knowing the volume of the solution and the amount
of solute dissolved in it, we can calculate the molarity of the prepared solution.
42. 42
Dilution of solutions: is the procedure for preparing a less
concentrated solution from a more concentrated solution.
Dilution
Add Solvent
Moles of solute
before dilution (i)
Moles of solute
after dilution (f)=
Mi Vi Mf Vf=
43. 43
e.g. How would you prepare 100.0 mL of 0.200 M HCl
from a stock solution of 4.00 M HCl?
MiVi = MfVf
Mi = 4.00 M Mf = 0.200 M Vf = 0.1000 L Vi = ? L
Vi =
MfVf
Mi
= 0.200 M x 0.1000 L
4.00 M
= 0.00500 L = 5.00 mL
Dilute 5.00 mL of acid with water to a total volume
of 100.0 mL.
44. 44
Gravimetric Analysis
an analytical technique based on the measurement of mass.
(a) A solution containing a known amount of NaCl in a beaker.
(b) The precipitation of AgCl upon the addition of AgNO3 solution from a
measuring cylinder.
(c) AgCl precipitate is filtered through a vacuum filtration, which allows the
liquid (but not the precipitate) to pass through.
Basic steps for gravimetric analysis
e.g.
Solution Stoichiometry
46. 46
Acid-Base Titrations
In titration, a solution of accurately known concentration, called
a standard solution, is added gradually to another solution of
unknown concentration, until the chemical reaction between the
two solutions is complete.
If we know the volumes of the standard and unknown
solutions, we can calculate the concentration of the unknown
one.
The acid often chosen for standardazation of bases is
potassium hydrogen phthalate (KHP), for which the molecular
formula is KHC8H4O4 (molar mass = 204.2 g)
The reaction between KHP and sodium
hydroxide is
KHC8H4O4(aq) + NaOH(aq) → KNaC8H4O4(aq) + H2O(l)
47. Indicator : substance that changes color (end point) at
(or near) the equivalence point.
Slowly add base
to unknown acid
UNTIL
the indicator
changes color
(End point)
Equivalence point : the point at which the acid has completely
reacted with or been neutralized by the base.
48. 48
e.g. What volume of a 1.420 M NaOH solution is
required to titrate 25.00 mL of a 4.50 M H2SO4
solution?
The chemical equation
volume acid moles acid moles base volume base
H2SO4 + 2NaOH 2H2O + Na2SO4
4.50 mol H2SO4
1000 mL soln
x
2 mol NaOH
1 mol H2SO4
x
1000 ml soln
1.420 mol NaOH
x25.00 mL = 158 mL
M
acid
rxn
coef.
M
base
49. other method
At the equivalence point
moles of NaOH = 2 x moles of H2SO4
(M V)NaOH 2= (M V)H2SO4
1.420 VNaOH = 2 x 4.50 x 25.00
VNaOH 158= mL
50. 50
e.g. The acidic substance in vinegar is acetic acid, HC2H3 O2.
When 4.00 g of a certain vinegar sample was titrated with
0.200 M NaOH, 25.56 mL of the NaOH solution were
required to reach the equivalence point. What is the
percent composition by mass of HC2H3O2 in the vinegar?
A) 7.67%
B) 30.7%
C) 76.8%
D) 3.84%
