NEET Chemistry: Electrochemical cells and Nernst equation Practice Questions

Correct answer: C — It is the electrode where oxidation occurs.

In any galvanic cell, oxidation occurs at the anode, which is the site where the loss of electrons (oxidation) takes place.

Correct answer: D — It increases because the reaction becomes more spontaneous.

For a reaction, increasing the temperature generally increases the spontaneity (makes it more favorable), leading to an increase in the standard cell potential (E°₍cell)) if the reaction is exothermic, or a change governed by the Gibbs-Helmholtz relationship.

Correct answer: A — To calculate the cell potential under non-standard conditions.

The Nernst equation is used to calculate the cell potential (E₍cell)) when the reaction is not under standard conditions, incorporating the effects of non-standard concentrations.

Correct answer: D — E = E° - RT/nF ln Q

The Nernst equation relates the non-standard cell potential (E) to the standard cell potential (E°) and the reaction quotient (Q), which is the ratio of product concentrations to reactant concentrations. The correct form is E = E° - RT/nF ln Q (or using base 10 logarithm, log Q).

Correct answer: C — Gibbs Free Energy

The electrical work done by a cell is related to the change in Gibbs Free Energy (ΔG = -nFE). This relationship is fundamental in electrochemistry.

Correct answer: C — E = E°

If Q = 1, the Nernst equation simplifies to E = E° - RT/nF ln(1) = E° - 0 = E°.

Correct answer: D — It is the driving force for the cell reaction.

Electron transfer is the core process in electrochemistry. The movement of electrons from the anode to the cathode is the mechanism that drives the non-spontaneous reactions, providing the electrical potential.

Correct answer: D — Negative

A process is spontaneous when the change in Gibbs Free Energy (ΔG) is negative (ΔG < 0). This is the fundamental thermodynamic criterion for spontaneity.

Correct answer: C — Reaction quotient (Q)

The Nernst equation involves the cell potential (E), the standard potential (E°), the number of electrons transferred (n), and the reaction quotient (Q) which depends on the concentrations of reactants and products.

Correct answer: C — ΔG° = -nFE°₍cell)

The relationship is ΔG° = -nFE°₍cell). This equation links the electrical potential to the thermodynamic energy change.

Correct answer: D — Zero

At equilibrium, the change in Gibbs free energy is zero, which implies that the cell potential under equilibrium conditions is zero if we consider the overall potential change relative to the standard state definition, or more simply, E=0 when expressed in terms of ΔG=0 for the reaction itself.

Correct answer: C — Mg(s) + Ag⁺(aq) → Mg²⁺(aq) + Ag(s)

The reaction Mg(s) + Ag⁺(aq) → Mg²⁺(aq) + Ag(s) has a standard cell potential (E°₍cell)) that is positive, indicating it is a spontaneous reaction under standard conditions.

Correct answer: D — Cell Potential (E₍cell))

The spontaneity of a reaction, including electrochemical cells, is fundamentally governed by the change in Gibbs Free Energy (ΔG). While the Nernst equation relates E₍cell) to ΔG°, the inherent spontaneity relates to ΔG (or ΔG° for standard conditions).

Correct answer: B — ΔG° = -nFE°

The standard Gibbs free energy change (ΔG°) is related to the standard cell potential (E°) and the Faraday constant (F) by the equation ΔG° = -nFE°. This relationship defines the thermodynamic driving force of the cell.