Question

Use the following pair of half-reactions to design a galvanic cell. Then write in the proper coefficient for each of the species involved in the overall reaction. Water molecules and protons are not shown in the half-reactions, but may need to be added to the overall reaction.

N2 (g)→N2H5+ (aq)

MnO4- (aq)→Mn2+ (aq)

Find coefficients for
MnO4- (aq)
N2 (g)
Mn2+ (aq)
N2H5+ (aq)
H+ (aq)
H2O (l)

Answer 1

In the galvanic cell using the given pair of half-reactions, the overall reaction is :

N2 (g) → coefficient = 1

MnO4- (aq) → coefficient = 1

Mn2+ (aq) → coefficient = 1

N2H5+ (aq) → coefficient = 1

H+ (aq) → coefficient = 8

H2O (l) → coefficient = 4

To design a galvanic cell using the given pair of half-reactions and write the proper coefficients for each species in the overall reaction:

1. Write the half-reactions:

N2 (g) → N2H5+ (aq)

MnO4- (aq) → Mn2+ (aq)

2. Balance the half-reactions:

For the N2 half-reaction, there are no atoms other than nitrogen, so it is already balanced.

For the MnO4- half-reaction, you need to add H+ (aq) to balance the hydrogen atoms and H2O (l) to balance the oxygen atoms.

Balanced MnO4- half-reaction:

MnO4- (aq) + 8H+ (aq) + 5e- → Mn2+ (aq) + 4H2O (l)

3. Determine the overall reaction:

To find the overall reaction, add the two balanced half-reactions together. The electrons on each side should cancel out.

Overall balanced reaction:

N2 (g) + MnO4- (aq) + 8H+ (aq) + 5e- → N2H5+ (aq) + Mn2+ (aq) + 4H2O (l)

4. Write the coefficients for each species in the overall reaction:

N2 (g) → coefficient = 1

MnO4- (aq) → coefficient = 1

Mn2+ (aq) → coefficient = 1

N2H5+ (aq) → coefficient = 1

H+ (aq) → coefficient = 8

H2O (l) → coefficient = 4