AP Chemistry: Electrochemistry 3

Question 1

The Nernst equation at 25 °C is E = E° − (0.0592/n) log Q. As Q increases, the cell potential:

Accepted Answer

Decreases

Answer

A larger Q makes the log term larger, subtracting more from E° and lowering E.

Question 2

When an electrochemical cell reaches equilibrium, the cell potential E equals:

Accepted Answer

0 V

Answer

At equilibrium no net reaction occurs, so the measured cell potential is zero.

Question 3

For a cell with n = 2 and E° = +0.46 V, what is log K at 25 °C?

Accepted Answer

About 15.5

Answer

log K = nE°/0.0592 = (2 × 0.46)/0.0592 ≈ 15.5.

Question 4

Increasing the concentration of reactant ions in the cathode compartment will generally:

Accepted Answer

Increase the cell potential

Answer

More cathode reactant lowers Q, which raises E according to the Nernst equation.

Question 5

A concentration cell generates voltage because of a difference in:

Accepted Answer

Ion concentration between the two half-cells

Answer

A concentration cell uses identical electrodes but differing ion concentrations to produce potential.

AP Practice Test