Question

What is the overall cell potential for this redox reaction? Ba + Ca2+ → Ba2+ + Ca Given: Ba2+ + 2e− → Ba(s) –2.90 and Ca2+ + 2e− → Ca(s) –2.87

Answer 1

Cell potential = potential of the cathode - potential of the anode
First you have to figure out what is the anode and cathode.
Anode has a higher reducing potential because anode is where oxidation occurs
-2.90 is lesser than -2.87
Therefore the anode should be the one with the -2.90 potential and the cathode is the one with -2.87
Cell potential = -2.87 - (-2.90 )
= -2.87 + 2.90
= 0.03 V

Answer 2

Ba + Ca2+ → Ba2+ + Ca


Ba → Ba2+ + 2e- oxid +2.90 V (reverse the reaction change the sign)
Ca2+ + 2e- → Ca red -2.87 V
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Ba + Ca2+ → Ba2+ + Ca E = +2.90V - 2.87 V = 0.03 V