Question

If 1.0 k cal of heat is added to 1.2 L of $O_2$ in a cylinder of constant pressure of 1 atm, the volume increases to 1.5 L. Calculate $\Delta H$ and $\Delta U$ of the process.

Answer 1

$\Delta U=q-P\Delta v$

$\Rightarrow \Delta U=1000-[1\times (1.5-1.2\left)\right]\times \mathrm{24.21.1.}Latm=24.21cal$

$\Rightarrow \Delta U=999.7cal$

or

$\Rightarrow \Delta U=99.3Kcal$

at constant pressure

$\Delta H=q_p=1Kcal$