Question

Exercise 18.46

Calculate the standard cell potential for each of the following electrochemical cells.

Part A

Ni2+(aq)+Mg(s)→Ni(s)+Mg2+(aq)

Ecell=

  V

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Part B

2H+(aq)+Fe(s)→H2(g)+Fe2+(aq)

Express your answer using two significant figures.

Ecell=

  V

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Part C

2NO−3(aq)+8H+(aq)+3Cu(s)→2NO(g)+4H2O(l)+3Cu2+(aq)

Express your answer using two significant figures.

Ecell=

  V

Answer 1

A)

Ni2+(aq)+Mg(s)?Ni(s)+Mg2+(aq)

Ni2+ + 2 e? ? Ni(s) ?0.25 (this will reduce, this is cathode)

Mg2+ + 2 e? ? Mg(s) ?2.372 (this will oxidize, this is anode)

E°cell = Ecathode - Eanode = -0.25 - -2.372 = 2.122 V

B)

2H+(aq)+Fe(s)?H2(g)+Fe2+(aq)

Fe2+ + 2 e? ? Fe(s) ?0.44

H+ cell is 0 by definition

so Fe oxidized...

E°cell = Ered - Eox = 0 - - 0.44 = 0.44 V

2NO?3(aq)+8H+(aq)+3Cu(s)?2NO(g)+4H2O(l)+3Cu2+

NO3?(aq) + 2 H+ + e? ? NO2(g) + H2O +0.80

Cu2+ + 2 e? ? Cu(s) +0.337

E°cell = 0.80 - 0.337 = 0.463 V