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conductometric titration
Polarographic technique is applied for the qualitative or quantitative analysis of electroreducible or oxidisable elements or groups.
It is an electromechanical technique of analyzing solutions that measures the current flowing between two electrodes in the solution as well as the gradually increasing applied voltage to determine respectively the concentration of a solute and its nature.
The principle in polarography is that a gradually increasing negative potential (voltage) is applied between a polarisable and non-polarisable electrode and the corresponding current is recorded.
Polarisable electrode: Dropping Mercury electrode
Non-polarisable electrode: Saturated Calomel electrode
From the current-voltage curve (Sigmoid shape), qualitative and quantitative analysis can be performed. This technique is called as polarography, the instrument used is called as polarograph and the current-voltage curve recorded is called as polarogram
content- Principle
Ilkovic equation
Construction and working of dropping mercury electrode and rotating platinum electrode
Applications
Polarography is a voltammetric technique in which chemical species (ions or molecules) undergo oxidation (lose electrons) or reduction (gain electrons) at the surface of a dropping mercury electrode (DME) at an applied potential. Polarography only applies to the DME.
Objective of polarography
Polarography is an electroanalytical technique that measures the current flowing between two electrodes in the solution (in the presence of gradually increasing applied voltage) to determine the concentration of solute and its nature respectively
Polarography is based upon the principle that gradually increasing voltage is applied between two electrodes, one of which is polarisable (dropping mercury electrode) and other is non-polarisable and current flowing between the two electrodes is recorded.
A sigmoid shape current-voltage curve is obtained from which half wave potential as well as diffusion current is calculated.
Diffusion current is used for determination of concentration of substance.
Half wave potential is characteristic of every element.
Ilkovic equation is a relation used in polarography relating the diffusion current (id) and the concentration of the non-polarisable electrode, i.e., the substance reduced or oxidised at the dropping mercury electrode (polarisable electrode).
Definitions of types of currents
1. Residual current (ir), 2. Migration current (im): , 3. Diffusion current (id) 4.Half wave potential 5. Limiting current (il)
Dropping mercury electrode- Dropping mercury electrode (DME) is a polarisable electrode and can act as both anode and cathode.
The pool of mercury acts as counter electrode,
i.e., anode if DME is cathode or
cathode if DME is anode.
The counter electrode is a non-polarisable electrode.
To the analyte solution, electrolyte like KCl is added i.e., 50-100 times of sample concentration.
Pure nitrogen or hydrogen gas is bubbled through the solution, to expel (remove) out oxygen.
Eg: If the analyte solution contains cadmium ions, then cadmium ions are discharged at cathode (-)
Cd2+ + 2e- → Cd
Then, gradually increasing voltage is applied to the polarographic cell and current is recorded.
Graph is plotted between voltage applied and current. This graph is called Polarograph and the apparatus is known as Polarogram.
The diffusion current produced is directly proportional to concentration of analyte and this is used in quantitative analysis.
The half wave potential is characteristic of every compound and this is used in qualitative analysis.
Graph is plotted between voltage applied and current. This graph is called Polarograph and the apparatus is known as Polarogram.
The diffusion current produced is directly proportional to concentration of analyte and this is used in quantitative analysis.
The half wave potential is characteristic of every compound
Polarographic technique is applied for the qualitative or quantitative analysis of electroreducible or oxidisable elements or groups.
It is an electromechanical technique of analyzing solutions that measures the current flowing between two electrodes in the solution as well as the gradually increasing applied voltage to determine respectively the concentration of a solute and its nature.
The principle in polarography is that a gradually increasing negative potential (voltage) is applied between a polarisable and non-polarisable electrode and the corresponding current is recorded.
Polarisable electrode: Dropping Mercury electrode
Non-polarisable electrode: Saturated Calomel electrode
From the current-voltage curve (Sigmoid shape), qualitative and quantitative analysis can be performed. This technique is called as polarography, the instrument used is called as polarograph and the current-voltage curve recorded is called as polarogram
content- Principle
Ilkovic equation
Construction and working of dropping mercury electrode and rotating platinum electrode
Applications
Polarography is a voltammetric technique in which chemical species (ions or molecules) undergo oxidation (lose electrons) or reduction (gain electrons) at the surface of a dropping mercury electrode (DME) at an applied potential. Polarography only applies to the DME.
Objective of polarography
Polarography is an electroanalytical technique that measures the current flowing between two electrodes in the solution (in the presence of gradually increasing applied voltage) to determine the concentration of solute and its nature respectively
Polarography is based upon the principle that gradually increasing voltage is applied between two electrodes, one of which is polarisable (dropping mercury electrode) and other is non-polarisable and current flowing between the two electrodes is recorded.
A sigmoid shape current-voltage curve is obtained from which half wave potential as well as diffusion current is calculated.
Diffusion current is used for determination of concentration of substance.
Half wave potential is characteristic of every element.
Ilkovic equation is a relation used in polarography relating the diffusion current (id) and the concentration of the non-polarisable electrode, i.e., the substance reduced or oxidised at the dropping mercury electrode (polarisable electrode).
Definitions of types of currents
1. Residual current (ir), 2. Migration current (im): , 3. Diffusion current (id) 4.Half wave potential 5. Limiting current (il)
Dropping mercury electrode- Dropping mercury electrode (DME) is a polarisable electrode and can act as both anode and cathode.
The pool of mercury acts as counter electrode,
i.e., anode if DME is cathode or
cathode if DME is anode.
The counter electrode is a non-polarisable electrode.
To the analyte solution, electrolyte like KCl is added i.e., 50-100 times of sample concentration.
Pure nitrogen or hydrogen gas is bubbled through the solution, to expel (remove) out oxygen.
Eg: If the analyte solution contains cadmium ions, then cadmium ions are discharged at cathode (-)
Cd2+ + 2e- → Cd
Then, gradually increasing voltage is applied to the polarographic cell and current is recorded.
Graph is plotted between voltage applied and current. This graph is called Polarograph and the apparatus is known as Polarogram.
The diffusion current produced is directly proportional to concentration of analyte and this is used in quantitative analysis.
The half wave potential is characteristic of every compound and this is used in qualitative analysis.
Graph is plotted between voltage applied and current. This graph is called Polarograph and the apparatus is known as Polarogram.
The diffusion current produced is directly proportional to concentration of analyte and this is used in quantitative analysis.
The half wave potential is characteristic of every compound
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Physical Chemistry
Potentiometry, Electrochemical cell, construction and working of indicator an...Vandana Devesh Sharma
Potentiometry - Electrochemical cell -Construction and working of reference (Standard hydrogen, silver chloride electrode and calomel electrode)
Indicator electrodes (metal electrodes and glass electrode)
Methods to determine end point of potentiometric titration
and applications
Potentiometry is the method to find the concentration of solute in
A given solution by measuring the potential between two Electrodes
(reference and Indicator electrode) . Potentiometric titration involves
the measurement of the potential of the indicator electrode and
reference electrode.
In potentiometric titration reference and indicator electrodes are
immersed in the solution of particular analyte (titrand) and
potential of indicator electrode is measured with relation to
reference electrode.
Titrant is added in analyte (Titrand) and change in potential is noted
down.
At the end point there is sharp change in potential on indicator
electrode.
Graph is plotted between the indicator electrode potential and
volume of titrant added.
This method is used for determination of sharp end point.
Types of Potentiometric Titration
1. Acid-base titration 2. Redox Titration 3.Complexometric titration 4. Precipitation Titration
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EDTA Titration
ESTIMATION OF THE RATE OF REACTION WILL BE DONE BASED ON THE POTENTIAL DIFFERENCE BETWEEN REFERENCE AND INDICATOR ELECTRODE. THE POTENTIAL OF THE REFERENCE ELECTRODE IS STABLE WHERE AS THE POTENTIAL OF THE INDICATOR ELECTRODE VARIES WITH THE POTENTIAL OF THE SOLUTION IN WHICH IT IS PLACED
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Physical Chemistry
Potentiometry, Electrochemical cell, construction and working of indicator an...Vandana Devesh Sharma
Potentiometry - Electrochemical cell -Construction and working of reference (Standard hydrogen, silver chloride electrode and calomel electrode)
Indicator electrodes (metal electrodes and glass electrode)
Methods to determine end point of potentiometric titration
and applications
Potentiometry is the method to find the concentration of solute in
A given solution by measuring the potential between two Electrodes
(reference and Indicator electrode) . Potentiometric titration involves
the measurement of the potential of the indicator electrode and
reference electrode.
In potentiometric titration reference and indicator electrodes are
immersed in the solution of particular analyte (titrand) and
potential of indicator electrode is measured with relation to
reference electrode.
Titrant is added in analyte (Titrand) and change in potential is noted
down.
At the end point there is sharp change in potential on indicator
electrode.
Graph is plotted between the indicator electrode potential and
volume of titrant added.
This method is used for determination of sharp end point.
Types of Potentiometric Titration
1. Acid-base titration 2. Redox Titration 3.Complexometric titration 4. Precipitation Titration
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EDTA Titration
ESTIMATION OF THE RATE OF REACTION WILL BE DONE BASED ON THE POTENTIAL DIFFERENCE BETWEEN REFERENCE AND INDICATOR ELECTRODE. THE POTENTIAL OF THE REFERENCE ELECTRODE IS STABLE WHERE AS THE POTENTIAL OF THE INDICATOR ELECTRODE VARIES WITH THE POTENTIAL OF THE SOLUTION IN WHICH IT IS PLACED
It is an electrochemical method of analysis used for the determination or measurement of the electrical conductance of an electrolyte solution by means of a conductometer.
Electric conductivity of an electrolyte solution depends on :
Type of ions (cations, anions, singly or doubly charged
Concentration of ions
Temperature
Mobility of ions
The main principle involved in this method is that the movement of the ions creates the electrical conductivity. The movement of the ions is mainly depended on the concentration of the ions.
The electric conductance in accordance with ohms law which states that the strength of current (i) passing through conductor is directly proportional to potential difference & inversely to resistance.
i =V/R
Conductometry is used to analyze ionic species and to monitor a chemical reaction by studying the electrolytic conductivity of the reacting species or the resultant products.
Conductometry is an electrochemical method of analysis involve the measurement of the electrical conductivity of a solution. The conductance is defined as the current flow through the conductor.
In other words, it is defined as the reciprocal of the resistance.
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Synthesis of Salicylic Acid, Organic Synthesis
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Stereochemistry Assignment
Succession in Ecosystems
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Soil formation
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Community Ecology
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Eco 4 soil physical and chemical properties Rabia Aziz
soil
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An Introduction to Ecology 2
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An Introduction to Ecology 1
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Chlamydomonas
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Organic Synthesis:
The Disconnection Approach
One Group C-C Disconnection of Alcohol and Alkene
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Organic Synthesis:
The Disconnection Approach
One Group C-C Disconnection of Alcohol and Alkene
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photo redox reactions
Synthesis of benzamide from benzyl chlorideRabia Aziz
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lab: Synthesis of benzamide from benzyl chloride
Synthesis of benzamide from benzyl chlorideRabia Aziz
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Synthesis of benzamide from benzyl chloride Lab
reducation of co2 and its application to environment. Rabia Aziz
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reducation of co2 and its application to environment
analytical techniques for estimation of organic compoundsRabia Aziz
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ANALYTICAL TECHNIQUES FOR ESTIMATION OF ORGANIC COMPOUNDS
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Stereochemistry of Organic Compounds
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Nobel Prize in Chemistry 2017
Joachim Frank
Cryo-Electron Microscopy
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BS-III
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
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.
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.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
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.
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.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
Deep Behavioral Phenotyping in Systems Neuroscience for Functional Atlasing a...Ana Luísa Pinho
Functional Magnetic Resonance Imaging (fMRI) provides means to characterize brain activations in response to behavior. However, cognitive neuroscience has been limited to group-level effects referring to the performance of specific tasks. To obtain the functional profile of elementary cognitive mechanisms, the combination of brain responses to many tasks is required. Yet, to date, both structural atlases and parcellation-based activations do not fully account for cognitive function and still present several limitations. Further, they do not adapt overall to individual characteristics. In this talk, I will give an account of deep-behavioral phenotyping strategies, namely data-driven methods in large task-fMRI datasets, to optimize functional brain-data collection and improve inference of effects-of-interest related to mental processes. Key to this approach is the employment of fast multi-functional paradigms rich on features that can be well parametrized and, consequently, facilitate the creation of psycho-physiological constructs to be modelled with imaging data. Particular emphasis will be given to music stimuli when studying high-order cognitive mechanisms, due to their ecological nature and quality to enable complex behavior compounded by discrete entities. I will also discuss how deep-behavioral phenotyping and individualized models applied to neuroimaging data can better account for the subject-specific organization of domain-general cognitive systems in the human brain. Finally, the accumulation of functional brain signatures brings the possibility to clarify relationships among tasks and create a univocal link between brain systems and mental functions through: (1) the development of ontologies proposing an organization of cognitive processes; and (2) brain-network taxonomies describing functional specialization. To this end, tools to improve commensurability in cognitive science are necessary, such as public repositories, ontology-based platforms and automated meta-analysis tools. I will thus discuss some brain-atlasing resources currently under development, and their applicability in cognitive as well as clinical neuroscience.
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 .
Richard's aventures in two entangled wonderlandsRichard 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.
3. Abstract: Conductometric titration is a type of titration in which the electrolytic
conductivity of the reaction mixture is continuously monitored as one reactant is added. The
equivalence point is the point at which the conductivity undergoes a sudden change. Marked
increases or decrease in conductance are associated with the changing concentrations of the
two most highly conducting ions—the hydrogen and hydroxyl ions.The method can be used for
titrating coloured solutions or homogeneous suspension (e.g.: wood pulp suspension), which
cannot be used with normal indicators. The conductometric titration curve is a plot of the
measured conductance or conductivity values as a function of the volume of the solution
added. The titration curve can be used to graphically determine the equivalence point.
1. Introduction:
Conductometry is a measurement of electrolytic conductivity to monitor a progress of chemical
reaction. Conductometry has notable application in analytical chemistry, where conductometric
titration is a standard technique. In usual analytical chemistry practice, the term conductometry
is used as a synonym of conductometric titration, while the term conductimetry is used to
describe non-titrative applications. Conductometry is often applied to determine the total
conductance of a solution or to analyze the end point of titrations that include ions.
Conductance:The powerof electrolytesto conductelectriccurrentsistermedconductivityor
conductance.
G = I/R
Unit of Conductance: Siemens(S)
The conductance of the solutionmainly depends on two factors:
1.Size of the ions: The conductivity of the solution is inversely proportional to the size of the
ions .If the size of the ions is increasing then the conductivity of the solution will decrease
because the mobility of the ions will decrease by increasing the size of the ions.
2. Temperature: By increasing the temperature, the mobility of the ions in the solution will
increase. So temperature has a direct effect on conductance of solution. E.g. by increasing the
temperature the conductance will increase and vice versa.
Conductance Increases When:
1. Greater charge of ions
2. Smaller size of ions
3. Higher concentration of ions
4. Lower resistance of the solution
4. Electrolytes:are electrovalent substances that form ions in solution which conduct an
electric current.
Electrolysis: the phenomenon of decomposition of an electrolyte by passing electric
current through its solution is termed electrolysis.
Electrolytic Cell: contains water solution of an electrolyte in which two metallic
rodes(electrodes) are dipped.
Strong Electrolyte:Astrong electrolyteis a solute that completely, or almost completely,
ionizes or dissociates in a solution. Strong acids, strong bases and mostly salts are strong
electrolytes. They are good conductors of electricity and have a high conductanceeven at low
concentration. Example:NaCl , HCl , HNO3, H2SO4, KCl , CuSO4 , ZnSO4 etc.
Weak Electrolyte:A weak electrolyte is a substance which forms ions in an aqueous
solution but does not dissociate completely. When dissolved, a weak electrolyte does not
disperse completely into ions. The solution instead contains both ions and molecules. They
have low value of equivalent conductance. Weak acids, weak bases and few salts are weak
electrolytes. Examples: HF, HC2H3O2 (acetic acid), H2CO3 (carbonic acid), H3PO4 (phosphoric
acid),
Specific Conductance (K): It is defined as “The conductance of one centimeter cube(cc)
of a solution of an electrolyte.”
Specific Conductance Increases with:
1. Ionic concentration
2. Speed of the ions
Units of Specific Conductance: ohm-1 cm-1, S cm-1
Molar conductance(u):it is defined as the conductance of all ions produced by one mole
(one gram molecular weight) of an electrolyte when dissolved in a certain volume (cc).
U= K*100/ M
Equivalent Conductance (A): it is defined as the conductance of an electrolyte
obtained by dissolving one gram equivalent of it in volume (cc) of water.
A = K V
5. Dilution: The volume of water in which a certain amount of the electrolyte is dissolved is
always measured in cubic centmeters (cc) and this is known as dilution.
2. Conductometric Titration:Conductometric titration is a type of titration
in which the electrolytic conductivity of the reaction mixture is continuously monitored as
one reactant is added. The equivalence point is the point at which the conductivity
undergoes a sudden change.
The principle of conductometric titration is based on the fact that during the titration, one of
the ions is replaced by the other and invariably these two ions differ in the ionic conductivity
with the result that conductivity of the solution varies during the course of titration. The
equivalence point may be located graphically by plotting the change in conductance as a
function of the volume of titrant added.
In order to reduce the influence of errors in the conductometric titration to a minimum, the
angle between the two branches of the titrationcurve should be as small as possible. If the
angle is very obtuse, a small error in the conductance data can cause a large deviation. The
following approximate rules will be found useful.
•The smaller the conductivity of the ion which replaces the reacting ion, the more
accurate will be the result.
•The larger the conductivity of the anion of the reagent which reacts with the
cation to be determined, or vice versa, the more acute is the angle of titration
curve.
•The titration of a slightly ionized salt does not give good results, since the conductivity
increases continuously from the commencement. Hence, the salt
present in the cell should be virtually completely dissociated; for a similar
reason; the added reagent should also be as strong electrolyte.
Conductometric Titration Curves are:
1.Strong Acid with a Strong Base, e.g. HCl with NaOH:
Before NaOH is added, the conductance is high due to the presence of highly mobile hydrogen
ions. When the base is added, the conductance falls due to the replacement of hydrogen ions
by the added cation as H+ions react with OH− ions to form undissociated water. This decrease in
the conductance continues till the
equivalence point. At the equivalence point, the solution contains only NaCl. Afterthe
equivalence point, the conductance increases due to the large conductivity of OH-ions.
6. 2. Weak Acid witha Strong Base,e.g. acetic acid with NaOH:
Initially the conductance is low due to the feeble ionization of acetic acid. On the addition of
base, there is decrease in conductance not only due to the replacement of H+ by Na+ but also
suppresses the dissociation of acetic acid due to common ion acetate. But very soon, the
conductance increases on adding NaOH as NaOH neutralizes the un-dissociated CH3COOH to
CH3COONa which is the strong electrolyte. This increase in conductance continuesraise up to
the equivalence
point. The graph near the equivalence point is curved due the hydrolysis of salt CH3COONa.
Beyond the equivalence point, conductance increases more rapidly with the addition of NaOH
due to the highly conducting OH−.
Conductometric titration of a weak acid (acetic acid) vs. a strong base (NaOH)
7. 3. Strong Acidwith a Weak Base, e.g. sulphuric acid with dilute ammonia:
Initially the conductance is high and then it decreases due to the replacement of H+. But after
the endpoint has been reached the graphbecomes almost horizontal, since the excess aqueous
ammonia is notappreciably ionised in the presence of ammonium sulphate.
4. Weak Acid witha Weak Base:
The nature of curve before the equivalence point is similar to the curve obtained by
titratingweak acid against strong base. After the equivalence point, conductance virtually
remains same as the weak base which is being added is feebly ionized and, therefore, is not
much conducting.
Conductometric titration of a weak acid (acetic acid) vs. a weak base (NH4OH)
8. Discussion: Upon dilution specific conductance decreases, while equivalent conductance
and molar conductance increases.
Increase in equivalent conductance in case of a weak electrolyte is due to increase in the
number of ions.
Advantages of Conductometric Titration:
The main advantages to the conductometric titration are its applicability to very dilute, and
coloured solutions and to system that involve relative incomplete reactions.
Application of Conductometric Titration:
It can be used for acid base, redox, precipitation, or complex titrations.
Determination of sulphur dioxide in air pollution studies.
Determination of soap in oil.
Determination of accelerators in rubber.
Determination of total soap in latex.
Specific conductance of water.
Conclusion:
The electrical conductance of a solution is a measure of the solution’s ability to conduct
electricity. The ability of a solution to conduct electric current decreases as the resistance of the
solution increases. Electricity is conducted in a solution by ions of electrolytes. Conductance of
electrolytes increases with the increase of temperature and concentration of electrolytes. The
conductance of a solution is the sum of the conductance of all the ions in the solution. The
conductance of an ion in solution is related to the charge, size and concentration of the ion.
Conductometry can be used to locate the end point of the titration. Conductometric titration is
useful for acid-base, precipitation, and complexation titrations.
REFERENCE:
1. Introduction to Chemical Analysis, Robert D.Braun
2. Fundamental of Analytical Chemistry, Skoog,west.
3. Essentials of Physical Chemistry,Arun Bahl,B.S.Bahl,G.D.Tull
4. www.tau.ac.il/.../Files/conductometry-titrations.pdf
5. https://www.reference.com/.../definition-weak-electrolyte-3b8e99e7130207...
6. https://www.stolaf.edu/depts/chemistry/courses/.../elec.htm
7. www.citycollegiate.com/chapter3b.htm
8. https://en.wikipedia.org/wiki/Molar_conductivity