Use standard reduction potentials (shown below) to calculate the potential of a nickel-cadmium cell that uses a basic electrolyte that has a 4.5 M hydroxide concentration. Cd(OH)2(s) + 2e- ? Cd(s) + 2OH-(aq) E

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Consider the following table of standard reduction potentials.

Half-reaction	E ^o (V)
Cu²⁺(aq) + 2e^? ? Cu(s)	+0.34
Pb²⁺(aq) + 2e^? ? Pb(s)	-0.126
Cd²⁺(aq) + 2e^? ? Cd(s)	-0.403
Zn²⁺(aq) + 2e^? ? Zn(s)	-0.76

Based on these values, which of the following choices represents the correct combination of cell reaction and standard cell potential?

	Cu²⁺(aq) + Cd(s) ? Cu(s) + Cd²⁺(aq), +0.06 V
	Cu²⁺(aq) + Zn(s) ? Cu(s) + Zn²⁺(aq), ?0.42 V
	Pb²⁺(aq) + Cd(s) ? Pb(s) + Cd²⁺(aq), +0.53 V
	Pb²⁺(aq) + Zn(s) ? Pb(s) + Zn²⁺(aq), +0.63 V

(a) Write the reactions for the discharge and charge of a nickel–cadmium (nicad) rechargeable battery. (b) Given the following reduction potentials, calculate the standard emf of the cell:

Cd(OH)₂(s) + 2 e^– Cd(s) + 2 OH^–(aq) E^°_red = –0.76 V

NiO(OH)(s) + H₂O(l) + e Ni(OH)₂(s) + OH^–(aq) E°_red = +0.49 V

(c) A typical nicad voltaic cell generates an emf of +1.30 V. Why is there a difference between this value and the one you calculated in part (b)? (d) Calculate the equilibrium constant
for the overall nicad reaction based on this typical emf value.