Question

What is the calculated value of the cell potential at 298K for an electrochemical cell with the following reaction, when the Cu2+ concentration is 7.38×10-4 M and the Al3+ concentration is 1.43 M ?

3Cu2+(aq) + 2Al(s)3Cu(s) + 2Al3+(aq)

Answer: V

The cell reaction as written above is spontaneous for the concentrations given: True or False?

Answer 1

The cell given is

3Cu+2 + 2 Al -----------------> 3Cu + 2Al+3

SRP of Cu+2/Cu = 0.34V

SRP of AL+3 /Al = -1.66V

Thus E0 cell = SRp of Cu -SRp of Al

= 0.34 V -(-1.66) V

= 2.000V

At the given concentrations the E cell is calculated using Nernst equation

E cell = E0 cell -[ 0.059/n ]log [Products ]/[reactants]

= 2.0 V - [0.059/6] log (1.43)² / (7.38x10^-4)³

= -7.70 V

As the E cell value is negative, the cell reaction is NON-SPONTANEOUS AT THE GIVEN CONCENTRATIONS

FALSE .