Thermodynamics and Thermochemistry 1 Question 62
65. For the reaction, $2 \mathrm{CO}+\mathrm{O}{2} \rightarrow 2 \mathrm{CO}{2} ; \Delta H=-560 \mathrm{~kJ}$. Two moles of $\mathrm{CO}$ and one mole of $\mathrm{O}{2}$ are taken in a container of volume $1 \mathrm{~L}$. They completely form two moles of $\mathrm{CO}{2}$, the gases deviate appreciably from ideal behaviour. If the pressure in the vessel changes from 70 to $40 \mathrm{~atm}$, find the magnitude (absolute value) of $\Delta U$ at $500 \mathrm{~K}$. ( $1 \mathrm{~L}$-atm $=0.1 \mathrm{~kJ})$
(2006, 3M)
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Solution:
- $\Delta H=\Delta U+\Delta(p V)=\Delta U+V \Delta p$
$$ \begin{aligned} \Rightarrow \quad \Delta U & =\Delta H-V \Delta p \ & =-560-1 \times 30 \times 0.1=-563 \mathrm{~kJ} \end{aligned} $$
