Electrode Potential and Energy Quiz

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Questions and Answers

What does the equation $E = Eo + \frac{RT \ln[Mn+]}{nF}$ represent?

The Nernst equation relating electrode potential to concentration (correct)

The formula for the free energy change in a chemical reaction

The relationship between voltage and current in a circuit

The equation for calculating total charge in a circuit

Why is the sign of $\Delta G$ negative for a spontaneous process?

Negative $\Delta G$ means the reaction will not proceed

It shows that the reactants are favored at equilibrium

Because spontaneous processes require energy input

It indicates that energy is released during the reaction (correct)

What does the Faraday constant (F) represent?

The number of moles in a standard solution

The volume of 1 mole of gas at standard conditions

The potential difference across a circuit

The total charge of one mole of electrons (correct)

In the equation $\Delta G = \Delta G^o + RT \ln K_c$, what does $K_c$ represent?

The equilibrium constant for a chemical reaction Signup and view all the answers

What does a positive electrode potential (E) imply about a reaction?

The reaction tends to be spontaneous Signup and view all the answers

What occurs at the anode during a galvanic cell operation?

Formation of Zn ions Signup and view all the answers

Which process occurs at the cathode in a galvanic cell?

Reduction of Cu Signup and view all the answers

What is the relationship between cell potential and the ability to do work in a galvanic cell?

Higher cell potential equates to more work Signup and view all the answers

What occurs when the overall cell reaction reaches equilibrium?

Cell potential becomes zero Signup and view all the answers

How is cell potential expressed?

In volts Signup and view all the answers

What is the outcome of the overall reaction in a galvanic cell?

Electrical energy is produced Signup and view all the answers

What is necessary to measure the single electrode potential?

Coupling with a standard reference electrode Signup and view all the answers

What kind of charge does the cathode carry during operation in a galvanic cell?

Positive charge Signup and view all the answers

What is the Nernst equation for single electrode potential when R, F, and T values are substituted?

E = Eo + 0.0591 log10[Mn+]/n Signup and view all the answers

How does the metal ion concentration affect the single electrode potential?

It is directly proportional to the potential. Signup and view all the answers

What is the purpose of a salt bridge in a galvanic cell?

To facilitate the flow of electrons without introducing extra potential. Signup and view all the answers

Which electrode in a galvanic cell undergoes oxidation?

Anode Signup and view all the answers

What occurs at the cathode of a galvanic cell?

Metal ions are reduced to solid metal. Signup and view all the answers

What does the liquid junction potential affect in a galvanic cell?

It contributes to the observed emf of the cell. Signup and view all the answers

What condition is indicated by the parameters of the Nernst equation?

Potential is directly proportional to both concentration and temperature. Signup and view all the answers

What occurs at the anode during the operation of a galvanic cell?

Metal ions are formed from solid metal. Signup and view all the answers

What does the vertical line in cell notation represent?

The interface between two solutions Signup and view all the answers

In a galvanic cell, where does oxidation occur?

At the anode Signup and view all the answers

How is the reduction potential at the anode expressed?

As a negative value Signup and view all the answers

What notation is used to represent the separation of different phases in a Daniel cell?

A single vertical line Signup and view all the answers

What does the arrow in cell notation indicate?

The flow of electrons Signup and view all the answers

Which of the following is true about the electrode potential?

It can be both positive and negative depending on the reaction Signup and view all the answers

What is represented by the notation Mn+|M?

The tendency of metal ions to discharge Signup and view all the answers

What is the oxidation potential of Zn|Zn++?

+0.76 V Signup and view all the answers

What is the reaction at the anode for the calomel electrode?

Hg(l) + Cl−(aq)  ½ Hg2Cl2(s) + e− Signup and view all the answers

Which factor influences the electrode potential of the calomel electrode?

Concentration of KCl solution Signup and view all the answers

What is the potential of the silver-silver chloride electrode at 25°C with 1M KCl?

0.2224V Signup and view all the answers

What describes the construction process of the silver-silver chloride electrode?

Electrolysis of an argentocyanide solution Signup and view all the answers

Which of the following is NOT an advantage of the calomel electrode?

High accuracy Signup and view all the answers

In which scenario can the silver-silver chloride electrode be effectively used?

For determining Eo values in chloride-free cells Signup and view all the answers

What type of electrodes respond only to specific ions in solution?

Ion selective electrodes Signup and view all the answers

What is the potential of the silver-silver chloride electrode in a saturated KCl solution at 25°C?

0.199V Signup and view all the answers

Study Notes

Electrical Energy and Electrode Potential

Electrical energy is the product of voltage and coulombs.
Total charge is determined by the number of moles of electrons passing through a circuit.
Total charge is calculated as the product of the number of moles of electrons (n) and Faraday's constant (F), which represents the charge contained in one mole of electrons.
Maximum electrical work (Wmax) is equal to the electrical work (Wele) and is calculated as -nFE, where E is the electrode potential.
The negative sign indicates that the electrical work is done by the system on the surroundings.
Maximum work is equal to the change in free energy (ΔG).
The free energy change due to the transfer of one mole of ions across the double layer is related to the electrode potential, with ΔG = -nFE.
For spontaneous processes, ΔG is negative, and E is positive, as both n and F are positive.

Standard Electrode Potential and Nernst Equation

For reactions where reactants and products are in their standard states, ΔGo = -nFEo.
The standard electrode potential (Eo) is positive for spontaneous processes.
ΔG is related to ΔGo and the equilibrium constant (Kc) by the equation ΔG = ΔGo + RT lnKc.
This equation can be rearranged to express the electrode potential (E) in terms of the standard electrode potential (Eo) and the concentrations of the oxidized and reduced forms: E = Eo - (RT/nF) ln([M]/[Mn+]).
For a metal electrode, [M] = 1, and the equation simplifies to the Nernst equation: E = Eo + (RT/nF) ln[Mn+].

Effect of Concentration and Temperature

The single electrode potential is directly proportional to both the metal ion concentration and the temperature, as these terms appear in the numerator of the Nernst equation.

Galvanic Cells and Electrode Reactions

A galvanic cell is formed when two electrodes in contact with suitable electrolytes are connected externally by a conducting material and internally by a salt bridge, generating an electric current.
Liquid-liquid contact between different electrolyte solutions introduces an additional potential called the liquid junction potential.
This potential can be reduced by connecting the electrolyte compartments through a salt bridge, where the liquid-liquid junction potentials at either end cancel out.
The electrode where oxidation occurs is called the anode, while the electrode where reduction occurs is called the cathode.

Daniel Cell Example

The Daniel cell can be represented as Zn(s) | ZnSO4(aq) || CuSO4(aq) | Cu(s).
At the anode: Zn(s) → Zn++(aq) + 2e− (oxidation).
At the cathode: Cu++(aq) + 2e− → Cu(s) (reduction).
Overall reaction: Zn(s) + Cu++(aq) → Zn++(aq) + Cu(s).
In a galvanic cell, the cathode has a higher potential than the anode.

EMF of a Cell

The potential difference between the two electrodes in a cell is called the cell potential or EMF (electromotive force), represented as 'EMF,' 'emf,' or 'Ecell.'
The cell potential is measured in volts and is larger when a given number of electrons can do a large amount of work.
The cell potential becomes zero when the overall cell reaction is at equilibrium, and the cell can no longer do work.
The EMF of a cell is the difference in the single electrode potentials of the two electrodes: Ecell = Ecathode - Eanode.
The cell potential can also be expressed in terms of the standard cell potential and the ratio of products to reactants: Ecell = Eocell + (0.0591/n) log10([Products]/[Reactants]).

Measurement of Single Electrode Potential

Single electrode potentials cannot be measured directly.
To determine a single electrode potential, the electrode is coupled with a standard reference electrode, such as a calomel electrode.
The cell potential (Ex) is measured, and since the potential of the reference electrode (Ecalomel) is known, the potential of the unknown electrode (e.g., Ezn++|Zn) can be calculated: Ezn++|Zn = Ecalomel - Ex.

Cell Notation and Cell Conventions

Phase boundaries (metal-solution interfaces) are denoted by a vertical line (|).
A double vertical line (||) represents the salt bridge.
An arrow indicates the flow of electrons.
The anode is written on the left side of the cell notation, while the cathode is on the right.

Sign Conventions

The electrode potential is generally expressed as a reduction potential.
The electrode at which reduction occurs with respect to the standard hydrogen electrode has a positive reduction potential and a negative oxidation potential.
The electrode at which oxidation occurs with respect to the standard hydrogen electrode has a positive oxidation potential and a negative reduction potential.

Calomel Electrode

The calomel electrode is represented as Hg | Hg2Cl2(sat), KCl(solution).
The reaction at the calomel electrode: ½ Hg2Cl2(s) + e−  Hg(l) + Cl−(aq).
The electrode potential of the calomel electrode depends on the concentration of KCl solution used.

Silver-Silver Chloride Electrode

The silver-silver chloride electrode is frequently used as a reference electrode for accurate potential measurements.
It is constructed by coating a platinum wire with silver and then partially converting it to silver chloride.
The electrode is reversible with respect to chloride ions and can be represented as Ag(s) | AgCl(s), KCl(aq).
The reaction: Ag(s) + Cl−(aq)  AgCl(s) + e−.
The potential of the silver-silver chloride electrode is 0.2224V at 25oC (1M KCl) and 0.199V at 25oC (saturated KCl).

Ion Selective Electrodes

Ion selective electrodes respond to specific ions in a solution, ignoring others.

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Description

Test your understanding of electrical energy, electrode potential, and the Nernst equation. This quiz covers key concepts such as maximum electrical work, charge calculations, and the relationship between free energy and electrode potential. Perfect for reinforcing your knowledge of electrochemistry principles.