Question

When the following oxidation–reduction reaction in acidic solution is balanced, what is the lowest whole-number coefficient for Cu2+(aq)?

Rb(s)+Cu2+(aq)→Rb+(aq)+Cu(s)

Select one:

a. 5

b. 4

c. 1

d. 3

e. 2

Answer 1

Rb in Rb has oxidation state of 0

Rb in Rb+ has oxidation state of +1

So, Rb in Rb is oxidised to Rb+

Cu in Cu+2 has oxidation state of +2

Cu in Cu has oxidation state of 0

So, Cu in Cu+2 is reduced to Cu

Reduction half cell:

Cu+2 + 2e- --> Cu

Oxidation half cell:

Rb --> Rb+ + 1e-

Balance number of electrons to be same in both half reactions

Reduction half cell:

Cu+2 + 2e- --> Cu

Oxidation half cell:

2 Rb --> 2 Rb+ + 2e-

Lets combine both the reactions.

Cu+2 + 2 Rb --> Cu + 2 Rb+

Balance Oxygen by adding water

Oxygen is already balanced

Hydrogen is already balanced

This is balanced chemical equation in acidic medium

Cu+2 + 2 Rb --> Cu + 2 Rb+

The coefficient of Cu2+ is 1

Answer: c.1