(a) Suppose that an alkaline battery was manufactured using cadmium metal rather than zinc. What effect would this have on the cell emf? (b) What environmental advantage is provided by the use of nickel-metal-hydride batteries over nickel-cadmium batteries?

To analyze the effect of using cadmium instead of zinc in an alkaline battery, we first need to compare their standard reduction potentials. The standard reduction potential for zinc is: \( Zn^{2+} + 2e^− \rightarrow Zn\); \(E^0 = −0.76 V\) And for cadmium: \( Cd^{2+} + 2e^− \rightarrow Cd\); \(E^0 = −0.40 V\) Higher standard reduction potential means higher tendency for the reduction to occur. Therefore, cadmium has a higher tendency to get reduced as compared to zinc. Now, let's calculate the difference in the cell emf if we were to replace zinc with cadmium. We can do this by subtracting the standard reduction potentials of zinc and cadmium: \(ΔE^0 = E^0_{Cd} - E^0_{Zn} = -0.40 V - (-0.76 V) = 0.36 V\) Since the difference is positive, the cell emf will be higher when using cadmium metal instead of zinc (by 0.36 V).

Nickel-metal-hydride (NiMH) batteries and nickel-cadmium (NiCd) batteries are both types of rechargeable batteries. The main difference between them is the materials used for their negative electrodes; NiCd batteries use cadmium while NiMH batteries use a metal alloy for their negative electrode. The environmental advantage of using NiMH batteries over NiCd batteries comes from the fact that cadmium is a toxic heavy metal. The disposal of NiCd batteries can lead to environmental pollution and harm, as cadmium can contaminate soil and water sources, posing a threat to both human health and wildlife. NiMH batteries, on the other hand, do not contain toxic heavy metals like cadmium. This makes them a more environmentally-friendly choice compared to NiCd batteries.