The standard half-cell potential for the reaction O2( g )+4H+( a q )+4e2H2O( l )

Question

The standard half-cell potential for the reaction
O2(g)+4H+(aq)+4e2H2O(l) is +1.229 V at 298.15 K.
The aO2 = 1.00 assuming that the aH+ is equal to the molality.

Part A

Calculate E for a 0.500-molal solution of H2SO4 for aO2 = 1.00 assuming that the aH+ is equal to the molality.

Part B

Calculate E for a 0.500-molal solution of H2SO4 for aO2= 1.00 using the measured mean ionic activity coefficient for this concentration from the data tables in the textbook.

Part C

How large is the relative error if the concentrations, rather than the activities, are used?

EXPLAIN AND SHOW CALCULATIONS PLEASE

Explanation / Answer

for the given cell reaction,

Part A) molality of H2SO4 = 0.5 m

Using Nernst equation,

E = Eo - 0.0592/n logK

    = 1.229 - 0.0592/4 log(1/(1)(0.5)^4)

    = 1.211 V

Part B) using mean activity coefficient

= (1 + 0.5)/2 = 0.75

E = Eo - 0.0592/n logK

    = 1.229 - 0.0592/4 log(1/(1)(0.75)^4)

    = 1.221 V

Part C) Calculation require concentration values

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