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SHEET 3

1- Consider a galvanic cell based on the reaction

Al+++(aq) + Mg(s) → Al(s) + Mg++(aq)

v37.2-=E

v66.1-=E

Mg++Mg

A l+++A l

→

→

Give the balanced cell reaction and calculate E° for the cell.

2- Describe completely the following galvanic cell based on the following half

reactions.

Cl2 + 2e- → 2 Cl- E°=1.36 v

Br2 + 2e- → 2 Br- E°= 1.09 v

3- Predict whether the following reaction would proceed spontaneously as

written at 298 K.

Co(s) + Fe++ (aq) → Co++(aq) + Fe(s)

Given that [Co++]=0.15 M and [Fe++]=0.68 M

v44.0-=E

v28.0-=E

Fe++Fe

C o++C o

→

→

4- Calculate the EMF for the cell based on the following half reactions

VO2 + 2 H+ + e- → VO++ + H2O E° = 1.00 v

Zn++ + 2 e- → Zn E° = -0.76 v

Where: T=25°C [VO2++]=2.0M

[H+]=0.5M [VO++]=1.0x10-2M

[Zn++]=1.0x10-1M

5- Consider the cell described below:

Zn|Zn++(1.00M) || Cu++(1.00 M)|Cu

2

Calculate the cell potential after the reaction has operated long enough for

the [Zn++] to have changed by 0.2 mol/L. (Assume T=25°C)

6- Calculate EMF of the following cell if v-0.76=EZn→++Zn

Zn(s)|Zn++(aq,0.1M)||Zn++(aq,1.0M)|Zn(s)

7- Calculate the [Cu++]/[Zn++] ratio at which the following reaction will

become spontaneous at 25°C.

Cu(s) + Zn++(aq) → Cu++(aq) + Zn(s)

8- Consider the following half reactions

MnO4-(aq) + 8 H+(aq) + 5e- → Mn++(aq) + 4 H2O (L) E°=1.51

NO3-(aq) + 4 H+(aq) + 3 e- → NO(g) + 2 H2O (L) E°=0.96

Predict whether NO3- ions will oxidize Mn2+ to MnO4

- under standard state

conditions.

9- How long will it take to plate out 1.0 kg Al from aq Al+++ with a current of

100.0 A? (M.wt. of Al=26.98).

10- What mass of Co from aq Co++ can be produced in 1.0 h with a current of

15 A? (M.wt. of Co= 59).

11-An unknown metal M is electrolyzed. It took 74.1 s for a current of 2.00 A

to plate out 0.107 g of the metal from a solution containing M(NO3)3.

Identify the metal.