Question

In a lab measuring electrochemical potential:

- would the measured potential of two electrodes of Cu/Cu^2+ (1M) and Cu/Cu^2+ (.1M) be equal to,or different from, zero? Why?

- can the potentials that are measured in the practice be considered standard potentials? Why?

- what happens when we vary the concentration using the information given by the Nernst equation?

Answer 1

a)

they should be DIFFERENT, since the potentials are mainly due to their quotient concentrations, i.e.

Ecell = E°cell - 0.0592/n*log(Q)

since E°cell and n are constant, only Q (quotient of concentraitons) can change.

b)

All cell potentials can be considered standards if you measue over the SAME potential, i.e. it is like a reference

c)

when we vary concentrations:

Ecell = E°cell - 0.0592/n*log(Q)

i.e. we mean Q

Q = [prducts]^p / [reactants]^r

therefore, we want to favour increase in reatants, so the Q decreass, so log(Q) decreases as well... this will favour the Ecell incrreas