Question

Consider the following reactions:

3 Ni 2+(aq) + 2Cr(OH)3 (s) + 10 OH –(aq) → 3 Ni (s) + 2 CrO4 –2 (aq) + 8 H2O (l)

A) What is the value for n for this reactions?

B) Calculate the standard Gibbs Free-Energy

C) How long does it take a current of 5 A to deposit 95 g of nickel?

Answer 1

For the reaction

3 Ni2+(aq) + 2 Cr(OH)3(s) + 10 OH- (aq)  →  3 Ni(s) + 2 CrO42-(aq) + 8 H2O(l) G = +87 kJ/mol

Given:

(Ni2+(aq) + 2 e- →  Ni(s)) x 3 Ered = -0.28 V

(CrO42-(aq) + 4 H2O(l) + 3 e- →  Cr(OH)3(s) + 5 OH-(aq)) x 2

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3 Ni2+(aq) + 6 e- →  3 Ni(s)

2 CrO42-(aq) + 8 H2O(l) + 6 e- →  2 Cr(OH)3(s) + 10 OH-(aq)