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Question

Calculating Concentrations in a Galvanic Cell

What is the pH of the solution in the cathode

compartment of cell when PH2 = 1.0 atm, [Zn2+] in the anode compartment is 0.10 M, and cell emf is 0.542 V? 

 

Answer 1

Step 1:

The chemical reaction is .

The partial pressure of H₂ is 1 atm.

Concentration of [Zn²⁺] = 0.10 M.

The emf of the cell is 0.542 v.

Nernst Equation :

The dependence of the cell emf on concentration can be obtained from the dependence of the free-energy change on concentration.

Nernst equation is , where is the reaction quotient.

For the reaction,

Step 2:

Calculate .

The cell potential (always positive for a galvanic cell) where  .

The direction of electron flow obtained by inspecting the half reactions and using the direction that gives a positive cell potential.

Anode :         

Cathode :                      

The cell potential .

Step 3:

Definition of pH: .

pH of the solution in cathode is 3.68.

Solution:

pH of the solution in cathode is 3.68.