Electrochemistry Flashcards
What is Electrochemistry?
It is a branch of physical chemistry that uses the measurement of electrical signals associated with chemical systems within and electrochemical cell.
What type of chemistry measures the inter conversion of electrical and chemical phenomena?
Electrochemistry
What is electrochemistry used for in clinical chemistry?
It is used to measure the concentrations of ions, drugs, hormones, metals, gases.
List the three main categories of electrochemistry.
Potentionmetry
Coulometry
Amperometry
What is an electrochemical cell?
An electrochemical cell is typically two electrodes that bridge between a chemical system and an electrical system
What is the device through which chemical energy changes to electrical energy?
Electrochemical cell
What does the electrochemical cell measure and what does it relate to?
It measures current or voltage and relates it to the concentration of a chemical species (like ions)
What does the chemical reaction create in an electrochemical cell system?
It creates a constant current between the two electrodes
What is the relationship between the amount of current and the amount of ions in the solution?
The amount of current is proportional to the amount of ions in the solution.
What do electrons flow away Fromm s to what do they flow to? What processes occur during these movements?
Electrons (e-) flow away from the anode = oxidation
and flow towards (accepted by) the cathode = reduction
Explain oxidation and reduction in terms of electron transfer
Oxidation refers to the loss of electrons while reduction is the gain of electrons.
Explain the principle behind electrodes
A metal placed into a solution of its own ions will produce a voltage potential relative to the concentration (or activity) of ions in the solution.
What are the two types of electrodes?
Indicator electrode
Reference electrode
What electrode is sensitive and responds to changes in concentration or activity of an ion species in the solution in which it is immersed?
Indicator electrode
What electrode has a constant ion concentration and potential created by this electrode? This electrode doesn’t change within the reaction so can be used as a reference to gauge how much the indicator electrode changes
A reference electrode
What must an indicator electrode only react with?
An indicator electrode must react only with the analyte of interest when immersed in the analyte solution.
What are the two conditions for and indicator electrode
- Must react only with the a analyte of interest
- Must be selective by responding to one specific ion
What are the two types of indicator electrode seen?
Ion selective membrane electrode
Liquid/polymer membrane electrode
What is the most common indicator electrode type used?
Ion selective membrane electrode
What does the ion selective membrane electrode do?
It measures the voltage potentials across a selective membrane, diffuses into the solution causing a charge separation.
How does the liquid/polymer membrane electrode work?
Measures K using a valinomycin ionophore to prevent interference from Na or H and increased permeability to K
What is valinomycin?
It is an ion transporter, neutral carrier that binds K in the center of a ring of oxygen atoms.
what are the conditions for a reference electrode?
- Must be self contained
- Must have stable, simple components and a constant potential
What is the use of the constant potential in reference electrodes?
The constant potential is what we are comparing/referencing the indicator electrode potential to
What are we comparing or referencing the indicator electrode’s potential to?
Constant potential of the reference electrode
What are the two common reference electrodes?
Saturated calomel electrode
Silver-silver chloride electrode
How does the saturated calomel electrode work?
In saturated calomel electrode, HgCl in a paste form is in contact with metallic Hg in an electrolyte solution of KCl to keep a constant concentration.
How does the silver-silver chloride electrode work?
The Ag-AgCl electrode has a AgCl-coated silver wire immersed in a solution or constant chloride concentration.
Define potentiometry.
It is the measurement of an electrical potential difference between two e,ectrodes immersed in a solution.
What is the measure of electrical voltage difference between two electrodes?
Potentiometry
It is defined as the use of electrodes to measures voltages from chemical reactions
Potentiometry
How are the electrodes in potentiometry characterized?
- A half-cell reaction: either oxidation or reduction
- A half-cell potential: quantitative measurement of the energy of a half-cell reaction relative to a reference electrode
What does the pH meter in potentiometry use to detect Hydrogen ions?
A specifically designed pH sensitive thin glass membrane
How does the pH meter looks at the concentration of hydrogen ions?
By measuring the potential/voltage difference between one half-cell and the other, that is the indicator electrode vs the reference electrode
What is the SI unit of charge?
Coulomb
Define coulomb
The amount of charge flowing
What is the base unit of electric current?
Ampere
Define ampere
The rate of flow of charge. That is how fast charge is moving over time (s)
What is 1 ampere in relation to a coulomb?
1 ampere is the flow of 1 coulomb of a charge per second. 1coulomb/1second
How is electrical current calculated?
Charge/time
What does coulometry measure?
Coulometry measures the electrical charge passing passing between two electrodes in an electrochemical cell.
What is the relation between the amount of charge and half cell reaction?
The amount of charge passing between two electrodes is directly proportional to the oxidation or reduction reaction at one of the electrodes
What is the term used to define the amount of electricity (in coulombs) consumed or produced in an electrochemical reaction?
Coulometry
How is the amount of electricity calculated? (In coulombs)
Current * time
What is coulometry used for?
Measures Cl amount in body fluids using the sweat chloride test which generates silver ions from a silver wire at the anode in the reaction.
