Thermodynamics C Question 8
Question 8 - 2024 (30 Jan Shift 2)
Two reactions are given below:
$2 \mathrm{Fe}{(\mathrm{s})}+\frac{3}{2} \mathrm{O}{2(\mathrm{~g})} \rightarrow \mathrm{Fe}{2} \mathrm{O}{3(\mathrm{~s})}, \Delta \mathrm{H}^{\circ}=-822 \mathrm{~kJ} / \mathrm{mol}$
$\mathrm{C}{(\mathrm{s})}+\frac{1}{2} \mathrm{O}{2(\mathrm{~g})} \rightarrow \mathrm{CO}_{(\mathrm{g})}, \Delta \mathrm{H}^{\circ}=-110 \mathrm{~kJ} / \mathrm{mol}$
Then enthalpy change for following reaction
$3 \mathrm{C}{(\mathrm{s})}+\mathrm{Fe}{2} \mathrm{O}{3(\mathrm{~s})} \rightarrow 2 \mathrm{Fe}{(\mathrm{s})}+3 \mathrm{CO}_{(\mathrm{g})}$
Show Answer
Answer (492)
Solution
$2 \mathrm{Fe}{(\mathrm{s})}+\frac{3}{2} \mathrm{O}{2(\mathrm{~g})} \rightarrow \mathrm{Fe}{2} \mathrm{O}{3(\mathrm{~s})}, \Delta \mathrm{H}^{\circ}=-822 \mathrm{~kJ} / \mathrm{mol} \ldots$ (1)
$\mathrm{C}{(\mathrm{s})}+\frac{1}{2} \mathrm{O}{2(\mathrm{~g})} \rightarrow \mathrm{CO}_{(\mathrm{g})}, \Delta \mathrm{H}^{\circ}=-110 \mathrm{~kJ} / \mathrm{mol} \ldots$ (2)
$3 \mathrm{C}{(\mathrm{s})}+\mathrm{Fe}{2} \mathrm{O}{3(\mathrm{~s})} \rightarrow 2 \mathrm{Fe}{(\mathrm{s})}+3 \mathrm{CO}{(\mathrm{g})}, \Delta \mathrm{H}{3}=$ ?
$(3)=3 \times(2)-(1)$
$\Delta \mathrm{H}{3}=3 \times \Delta \mathrm{H}{2}-\Delta \mathrm{H}_{1}$
$=3(-110)+822$
$=492 \mathrm{~kJ} / \mathrm{mole}$
