Question

what is the balanced oxidation half-reaction for the following unbalanced redox reaction:
ca(s) + ag⁺(aq) à ca²⁺(aq) + ag(s)

a. ca → ca²⁺ + 2 e-

b. ca → ca²⁺ + 2 e-

c. 2e- + ca → ca²⁺

d. 2 ag⁺ + 2 e- → 2ag

e. cannot be determined

Explanation:

1. First, identify oxidation: Oxidation is loss of electrons (LEO). In the reaction, Ca(s) goes to \(Ca^{2+}(aq)\). The oxidation state of Ca in Ca(s) is 0, and in \(Ca^{2+}\) it is +2. So Ca is oxidized (loses electrons).
2. Now, balance the oxidation half - reaction: The atom Ca is already balanced (1 Ca on each side). To balance charge, Ca (oxidation state 0) becomes \(Ca^{2+}\) (oxidation state +2), so it loses 2 electrons. The half - reaction is \(Ca

ightarrow Ca^{2 +}+2e^-\).

1. Analyze the options:

• Option c: Has electrons on the reactant side, which would be reduction (gain of electrons), so incorrect.
• Option d: Is a reduction half - reaction (Ag⁺ gains electrons to form Ag), so incorrect.
• Option e: We can determine the oxidation half - reaction, so incorrect.
• Options a and b (assuming it's a typo and they are the same) represent the correct oxidation half - reaction as Ca is oxidized, losing 2 electrons to form \(Ca^{2+}\).

Answer:

a. \(Ca
ightarrow Ca^{2+}+2e^-\) (and b. \(Ca
ightarrow Ca^{2+}+2e^-\) as they seem to be the same option, likely a typo. The correct oxidation half - reaction is \(Ca
ightarrow Ca^{2+}+2e^-\))