Question

1. Calculate the equilibrium constant Keq for the following reaction at 25°C: 3Fe2+(aq) + 2Cr(s) ↔ 3Fe(s) + 2Cr3+(aq)

3.8 x 10–31

7.2 x 10–11

1.4 x 1010

2.6 x 1030

1.6 x 1015

2. A 1M aqueous solution of copper(II) nitrate is electrolyzed. What are the predicted products at the anode and cathode?

N2 gas at the anode; copper metal at the cathode

O2 gas at the anode; copper metal at the cathode

NO2 gas at the anode; copper metal at the cathode

O2 gas at the anode; H2 gas at the cathode

NO2 gas at the anode; H2 gas at the cathode

Answer 1

1)

from data table:

Eo(Cr3+/Cr(s)) = -0.74 V

Eo(Fe2+/Fe(s)) = -0.44 V

As per given reaction/cell notation,

cathode is (Fe2+/Fe(s))

anode is (Cr3+/Cr(s))

Eocell = Eocathode - Eoanode

= (-0.44) - (-0.74)

= 0.300 V

here, number of electrons being transferred, n = 6

Eo = (2.303*R*T)/(n*F) log Kc

At 25 oC or 298 K, R*T/F = 0.0592

So, Eo = (0.0592/n)*log Kc

0.3 = (0.0592/6)*log Kc

log Kc = 30.4054

Kc = 2.6*10^30

Answer: 2.6*10^30

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