For the electrochemical cell, Mg(s) Mg^(2+) aq,1 M Cu^(2+) aq,1 M Cu s the standard emf of the cell is 2.70 V at 300 K. When the concentration of…

Question

For the electrochemical cell, Mg(s) Mg^(2+) aq,1 M Cu^(2+) aq,1 M Cu s the standard emf of the cell is 2.70 V at 300 K. When the concentration of Mg^(2+) is changed to x M, the cell potential changes to 2.67 V at 300 K. The value of x is ________. (given, F/R =11500 K V^(−1) , where F is the Faraday constant and R is the gas constants, ln 10 = 2.30 )

MARKS Content Team · Accepted Answer

Correct answer: 10. Mg s + Cu^(2+) aq →Mg^(2+) aq + Cu s E cell o = 2.70, E_cell = 2.67, Mg^(2+) = xM, Cu^(2+) = 1 M E_cell = E cell o − RT/nF ln x 2.67 = 2.70 − RT/2F ln x −0.03 = − (R × 300)/2F × ln x ln x = (0.03 × 2)/300 × F/R = (0.03 × 2 × 11500)/(300 × 1) ln x = 2.30 = ln 10 x = 10

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