Question

1. AA, AAA, C and D cells all deliver the same voltage( 1.5V) when the batteries are fully charged. However,as the size of the battery increases, the amount of current that can be deliveredby the battery also increases. What is the difference inside these bateries that accounts for the increase in current with size? Expalin.
2. The overall reaction for alkaline battery is given by
Zn(s)+ MnO2(s)+H2O(l)--> ZnO(s) + Mn(OH)2(s)
Does matallic zinc functon as the anode or the cathode in this system?

Answer 1

Answer:

A. The increase in size of the battery results in a smaller internal resistance and hence, a larger current delivery.

B. Zinc serves as the anode

Explanation:

A. The current that a battery can deliver is affected by the internal resistance of the battery.

The internal resistance resistance, r, is the resistance to flow of current within the battery. The smaller the internal resistance for a given emf, the more current and the more power the source can supply.

The relationship between current, I, emf, E, the external load ,R, and internal resistance is given by the equation:

I = E / (R + r)

The bigger the size of a battery, the smaller its internal resistance and thus, the larger the current the battery can deliver.

B. In a battery, the cathode is reduced by accepting electrons from the anode, while the anode is oxidized to zinc ion by giving up its electrons to the cathode.

From the equation of the reaction, metallic zinc is oxidized by giving up two electron to the cathode.

Zn(s) ----> Zn2+ + 2e-

Therefore, metallic zinc serves as the anode.