Consider the following reactions at 1000°C.
(I) Zn(s) + 1/2 O2(g) ZnO(g); = -360 kJ mol^-1
(II) C(s) + 1/2 O2(g) CO(g); = -460 kJ mol^-1
and choose the correct statement at 1000°C.

Question

Consider the following reactions at 1000°C.
(I) Zn(s) + 1/2 O2(g) $\rightarrow$ ZnO(g); $\Delta G^\circ$ = -360 kJ mol^-1
(II) C(s) + 1/2 O2(g) $\rightarrow$ CO(g); $\Delta G^\circ$ = -460 kJ mol^-1
and choose the correct statement at 1000°C.

Prashant Kotian · Accepted Answer

Correct answer: B. Step 1: Write down the net reaction for the reduction of ZnO by Carbon: ZnO(s) + C(s) -> Zn(s) + CO(g). Step 2: Calculate the standard Gibbs free energy change (ΔG°_reaction) for this net reaction: ΔG°_reaction = ΔG°_f(CO) - ΔG°_f(ZnO) = -460 kJ/mol - (-360 kJ/mol) = -100 kJ/mol. Step 3: Since the net Gibbs free energy change is negative (-100 kJ/mol), the reduction of ZnO by Carbon is thermodynamically spontaneous at 1000°C, meaning ZnO can be reduced to Zn by C (option b).

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