Answer:
The unbalanced half-reaction in which a species is reduced can be identified by looking for the reaction that involves the gain of electrons. Let's analyze each option to determine the correct answer:
a. C(s) → CO(g): In this reaction, carbon (C) is oxidized, not reduced. It loses electrons, so it is not the correct answer.
b. SO42- (aq) → H2S (g): In this reaction, sulfur (S) is reduced. It gains electrons from the hydrogen (H) atoms to form hydrogen sulfide (H2S). This is the correct answer.
c. Al(s) → Al3+ (aq): In this reaction, aluminum (Al) is oxidized, not reduced. It loses electrons, so it is not the correct answer.
d. 2 I- (aq) → I2(s): In this reaction, iodide ions (I-) are oxidized, not reduced. They lose electrons to form iodine (I2), so it is not the correct answer.
e. Cr2O3 (s) → CrO42- (aq): In this reaction, chromium (Cr) is reduced. It gains electrons to form chromate ions (CrO42-). This is also a correct answer.
Therefore, the unbalanced half-reactions in which a species is reduced are b. SO42- (aq) → H2S (g) and e. Cr2O3 (s) → CrO42- (aq).
Step-by-step explanation:
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