Question

) The cell reaction for a certain alkaline dry cell is

Zn(s)+2MnO2(s)+H2O(l)→Zn(OH)2(s)+Mn2O3(s

Which of the following statements concerning this cell is/are incorrect?

1.MnO2(s)   is oxidized to  Mn2O3(s)   during cell discharge.

2.Water is consumed during the discharge of this cell.

3.Zn(OH)2(s)   forms at the anode during discharge of this cell.

a. 1 only

b. 2 only

c. 3 only

d. 2 and 3

e. 1, 2 and 3

Answer 1

OPTION A. In the given reaction, from the balancing coefficients, it can be seen that water is also involved in the cell reactions. Taking the oxidation state changes of Zn and Mn the former changes from elemental state (0 oxidation state) to +2 state while Mn goes from +4 to +3 state (oxide ion has a charge of -2). Thus, Zn is oxidised while Mn is reduced. In all cells, oxidation occurs at the anode and reduction occurs at the cathode. So at the anode, the Zn gets oxidised to zinc hydroxide. Hence, among the given statements, only 2 and 3 are correct leaving only 1 incorrect as Mn is reduced in the cell.