Question

2. Consider the following rechargeable battery: Zn (s) ZnCl, (aq) ICI (aq) lai, o C (6) 2.a. (5 p) Write the reduction reaction corresponding to each half-cell. 2.b (p) Indicate the electrode from which the electrons will flow from the direction of the flow of the electrons in the circuit). To justify your answer, consider the electrode potential values to be similar to the corresponding Evalues. Refer to Appendix H in the textbook to find the E' values. 2.c. (5 p) How many kilograms of Clz will be consumed if the battery delivers a constant current of 1.00 x 10' A for 1.00 hour?

Answer 1

1)

The reduction reaction corresponding to each half cell are:

Zn²⁺ + 2e^- -----------------> Zn E^o = -0.76 V

Cl₂ + 2e^- ------------------> 2Cl^- E^o = 1.36 V

2)

Oxidation happens at anode (generation of electrons) while reduction happens at the cathode (consumption of electrons). The electron flow from anode to cathode in the external circuit

3)

Given current, I = 1 x10³ A

time = 1 hour = 60*60 = 3600 s

Charge, Q = I x t = 1*10³*3600

= 3.6 x 10⁶ C

But Q = nF

where n is the number of moles of electrons and

F is the Faraday constant = 96500

Therefore

number of moles of electrons, n = Q/F

= 3.6*10⁶/96500

= 37.3 moles

1 mole of chlorine consumes two moles of electrons. Therefore

number of moles of chlorine consumed = 37.3/2

= 18.65 moles

Molecular weight of Chlorine = 70.9 g

Therefore mass of chlorine consumed = 18.65 * 70.9

= 1.32 x 10³ g

Therefore mass of chlorine consumed = 1.32 kg