3pb2+(aq) + 2cr(s) → 3pb(s) + 2cr3+(aq) what is the number of moles of electrons gained by 3.0 moles of lead ions?

6 moles of Electrons

Explanation: balanced equation: 3 Pb+2(aq) + 2 Cr(s)> 3 Pb(s) + 2 Cr+3(aq)

Here oxidation no of Cr changes from 0 to +3 hence total no of electrons lost by Cr are 6 since one mole of Cr =3 Electrons lost ,and 2 moles of Cr =2x3=6 moles of Electrons.

These 6 moles of electrons lost by Cr are gained by 3 moles of Pb+2 and gets reduced into Pb.

So total 6 moles of Electrons are involved in Redox reaction