For the reaction 3Fe(s) + C(s) $\rarr$Fe₃C(s), $\Delta$H^$\circ$ = 21 kJ/mol and $\Delta$S^$\circ$ = 20.4 J/mol·K at 25^$\circ$C. Estimate the minimum temperature above which the formation of cementite (Fe₃C) is favored.

Question

Quizplus · Accepted Answer

The reaction is favored at higher temperatures because $\Delta$S^$\circ$ is positive. At 25^$\circ$C, $\Delta$G^$\circ$ = $\Delta$H^$\circ$ - T$\Delta$S^$\circ$ = 21 kJ/mol - (298 K)(20.4 J/mol·K) = 12.7 kJ/mol. Therefore, the reaction is not favored at 25^$\circ$C. To estimate the minimum temperature above which the reaction is favored, we can set $\Delta$G^$\circ$ = 0 and solve for T:0 = 21 kJ/mol - T(20.4 J/mol·K)T = 21 kJ/mol / (20.4 J/mol·K) = 1029 K = 756^$\circ$CTherefore, the minimum temperature above which the formation of cementite is favored is approximately 760^$\circ$C.

For the Reaction 3Fe(s) + C(s) →\rarr→ Fe3C(s) Δ\DeltaΔ H ∘\circ∘ = 21 KJ/mol And

For the Reaction 3Fe(s) + C(s) $\rarr$ Fe₃C(s) $\Delta$ H^$\circ$ = 21 KJ/mol And