What initial concentration of Cd2+ is required to result in a cell potential of 0.200 V in a voltaic cell constructed by connecting a nickel electrode that is dipped into 1.00 M NiSO4 solution to a cadmium electrode that is dipped into a solution containing the Cd2+ ions?

Answer 1

Cd ==> Cd^2+ + 2e Eo = ?
Ni^2+ + 2e ==> Ni E =-0.25
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Cd + Ni^2+ ==> Cd^2+ + Ni Ecell=0.2

Look up the Eo value for Cd^2+ and reverse it. Look up the Eo value for Ni since the Eo value is the definition for 1 M solution. You want the total for Ecell to be 0.200 so
EoCd + EoNi^2+ = 0.200 or
x + Eo Ni^2+ = 0.200 and solve for x. Then plug that value into the Nernst equation and solve for (Cd^2+). Post your work if you get stuck.