Question

Balance the following redox reaction if it occurs in acidic solution. What are the coefficients in front of Pb and H+ in the balanced reaction?

Pb2+(aq) + NH+4(aq) → Pb(s) + NO−3(aq)

Pb = 1, H+ = 8

Pb = 3, H+ = 5

Pb = 4, H+ = 10

Pb = 2, H+ = 3

Pb = 1, H+ = 2

Please explain how to get answer.

Answer 1

Pb+2 --> Pb

Pb atoms are balanced , so balance the charge

Pb+2 + 2e- ---> Pb

now

consider the other half reaction

NH4+ --> NO3-

balance the O atoms using H20

NH4+ + 3 H20 --> NO3-

balance the H atoms using H+

NH4+ + 3 H20 --> N03- + 10 H+

now balance the charge using electrons

NH4+ + 3 H20 --> N03- + 10 H+ + 8e-

now using common multiples , equate the electrons in both

NH4+ + 3 H20 --> NO3- + 10 H+ + 8e-

4 Pb+2 + 8e- --> 4 Pb

so the balanced reaction is

4 Pb+2 + NH4+ + 3 H20 --> 4 Pb + N03- + 10H+

so

the answer is

Pb = 4 , H+ = 10