A.) Consider the galvanic cell, Fe(s) | Fe 2 +(aq) | | Pb 2+ (aq) | Pb(s). Which

Question

A.) Consider the galvanic cell, Fe(s) | Fe 2 +(aq) | | Pb 2+ (aq) | Pb(s). Which one of the following changes to the cell would cause the cell potential to increase (i.e., become more positive)?   

increase the mass of Fe(s)

B.) Silver can be plated out of a solution containing Ag+ according to the half-reaction .   Ag+(aq)+eAg(s).   How much time (in minutes) does it take to plate 19 g of silver using a current of 3.5 A ?

increase the mass of Fe(s)

B.) Silver can be plated out of a solution containing Ag+ according to the half-reaction .   Ag+(aq)+eAg(s).   How much time (in minutes) does it take to plate 19 g of silver using a current of 3.5 A ?

Explanation / Answer

The Nernst equation for this cell is:
E = E° - (0.059/n)log[Fe 2+]/ [Pb 2+]

The log part is the one we will focus on, we need a higher [Fe 2+] to make the log value bigger (since Fe2+ is in the top of the division) and thus the cell potential will increase.

So the answer is:
increase the [Fe 2+] concentration

B. W = Z x i x t

{ W ammount of a substance deposite, i = current , t = time , Z = eq. wt of the substance/96500 }

19 g = (107.86 g / 96500) x 3.5 A x t

t = 4856.82 s = 80.94 minutes

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