AP Chemistry Unit 9.10 Nonstandard Cell Potential

[Maximum number: 2]

Metal-air cells are a relatively new type of portable energy source consisting of a metal anode, an alkaline electrolyte paste that contains water, and a porous cathode membrane that lets in oxygen from the air. A schematic of the cell is shown above. Reduction potentials for the cathode and three possible metal anodes are given in the table below.

(a)

The zinc-air cell is taken to the top of a mountain where the air pressure is lower.

[ 2 ]

(i)

Will the cell potential be higher, lower, or the same as the cell potential at the lower elevation?

[ 1 ]

(ii)

Justify your answer to part (c)(i) based on the equation for the overall cell reaction and the information above.

[ 1 ]

(\mathrm{O}_{2}(g)\), a reactant in the cell reaction, will be at a
lower partial pressure at the higher elevation;
thus
the reaction has a greater value of Q (closer to K ).
Deviations in partial pressure that take the cell
closer to equilibrium will decrease the magnitude
of the cell potential.

1 point is earned for a justification that relates a
lower pressure (or concentration) of $\mathrm{O}_{2}(g)$ to Q,
or a qualitative approach using the Nernst
equation.

AP Chemistry 9.10 Cell Potential Under Nonstandard Conditions Questions

Covered syllabus points

Covered syllabus points

Question 1

Question (a)

Question (i)

Question (ii)