Question

Calculate the standard emf for the cell if standard electrode potentials (reduction) Pb²⁺|Pb and Zn²⁺|Zn electrodes are -0.126 V and -0.763 V respectively.

a) -0.889 V
b) 0.889 V
c) -0.637 V
d) 0.637 V

Answer 1

The standard emf for the cell with given reduction potentials for Pb²⁺|Pb and Zn²⁺|Zn is calculated using the standard cell potential equation, resulting in an answer of 0.889 V, which indicates a spontaneous cell.

Step-by-step explanation:

To calculate the standard emf for the cell with the standard electrode potentials for Pb²⁺|Pb (-0.126 V) and Zn²⁺|Zn (-0.763 V), you will need to use the standard cell potential formula: Ecell = Ecathode - Eanode. Here, we need to identify which electrode serves as the cathode (reduction) and which as the anode (oxidation) in the cell. Generally, the more positive electrode potential serves as the cathode and the more negative one as the anode in a voltaic (galvanic) cell.

In this case, the Pb²⁺|Pb electrode has the less negative reduction potential, so it will serve as the cathode. The Zn²⁺|Zn electrode will be the anode. The standard emf of the cell is calculated as follows:

Ecell = EPb²⁺|Pb - EZn²⁺|Zn
Ecell = (-0.126 V) - (0.763 V)
Ecell = -0.889 V

The correct answer to the question is therefore 0.889 V since standard emf values are expressed as positive when the cell is spontaneous.