Given the balanced ionic equation:
3Pb2+ + 2Cr ==> 3Pb + 2Cr3+
What is the number of moles of electrons gained by 3.0 moles of lead ions?
(1) 5.0 mol (3)3.0 mol
(2) 2.0 mol (4) 6.0mol

Answer : The correct option is, (4) 6.0 molExplanation :The given balanced ionic equation is,[tex]3Pb^{2+}+2Cr\rightarrow 3Pb+2Cr^{3+}[/tex]In this reaction, lead undergoes reduction and chromium undergoes oxidation.Oxidation reaction : It is the reaction in which a substance looses its electrons. In this oxidation state increases.
Reduction reaction : It is the reaction in which a substance gains electrons. In this oxidation state decreases.Half reactions of oxidation and reduction are :
Oxidation : [tex]2Cr\rightarrow 2Cr^{3+}+6e^-[/tex]
Reduction : [tex]3Pb^{2+}+6e^-\rightarrow 3Pb[/tex]From the reduction reaction, we conclude that 6 moles of electrons gained by the 3 moles of lead ions.Hence, the correct option is, (4) 6.0 mole

answer:  6......................