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Question
Answer the following:
Predict whether the following reaction would occur spontaneously under standard state condition.
`"Ca"_(("s")) + "Cd"_(("aq"))^(2+) -> "Ca"_(("aq"))^(2+) + "Cd"_(("s"))`
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Solution
`"Ca"_(("s")) + "Cd"_(("aq"))^(2+) -> "Ca"_(("aq"))^(2+) + "Cd"_(("s"))`
At anode: `"Ca"_(("s")) -> "Ca"_(("aq"))^(2+) + 2"e"^(-)`
At cathode: `"Ca"_(("aq"))^(2+) + 2"e"^(-) -> "Cd"_(("s"))`
From the electrochemical series we have,
`"E"_"Ca"^circ` = - 2.866 V and `"E"_"Cd"^circ` = - 0.403 V
For cell having Ca as anode and Cd as cathode.
`"E"_"cell"^circ = "E"_"Cd"^circ - "E"_"Ca"^circ`
= - 0.403 V - (- 2.866) V
`"E"_"cell"^circ` = 2.463 V
Emf of cell being positive, the given cell reaction is spontaneous.
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