Final answer:
Two electrons are transferred in the oxidation half-reaction of copper, as shown by Cu(s) → Cu²⁺ (aq) + 2e−. Hence, the correct answer is B) 2.
Step-by-step explanation:
The question is how many electrons are transferred in the oxidation half-reaction of copper(Cu). The oxidation half-reaction given is Cu(s) → Cu²⁺ (aq) + 2e−. The number of electrons transferred in this reaction is clearly shown as 2 (two) electrons, which is represented by the coefficient '2' in front of the 'e−' in the chemical equation. Therefore, the correct answer is B) 2.
When combining the oxidation and reduction half-reactions to write the overall reaction, for every Cu atom that is oxidized (loses two electrons), two Ag⁺ ions are reduced (each gains one electron). Since we need 2 electrons for the reduction of two Ag⁺ ions, the half-reactions are already balanced in terms of electron transfer, and no further multiplication is necessary. Combining them provides the overall reaction: 2 Ag⁺ (aq) + Cu(s) → 2 Ag(s) + Cu²⁺ (aq).