Question

A one litre flask containing $N{H}_3\left(g\right)$ at 2.0 atmoshpere and 300 K is connected to another 800 mL flask containing HCl(g) at 8.0 atmosphere and 300 K by means of a narrow tube of negligible volume and gases were allowed to react quantitatively as :
$N{H}_3\left(g\right)+HCl\left(g\right)\to N{H}_{4}Cl\left(s\right);\Delta H=-43kJ/mol$
If heat capacity of HCl (g) $C_v$ is 20 $J{K}^{-1}mo{l}^{-1}$, determine final pressure inside the flask k assuming negligible heat capacity of flask and negligible volume of solid $N{H}_{4}Cl$.

Answer 1

$N{H}_3\left(g\right)+HCl\left(g\right)\to N{H}_{4}Cl\left(s\right)$
Mole 0.08 0.26 0
0 0.18 0.08
$\Rightarrow Q=0.08\times 4300=3440J$
Also, $Q=n{C}_v\Delta T\Rightarrow \Delta T=\frac{3440}{0.18\times 20}=955.55$
$T_{final}\left(T_{\ast 2}\right)=1255.55K$
$P_{final}\left(P_{\ast 2}\right)=\frac{0.18\times 0.082\times 1255.55}{1.8}$
$=10.3$ atmosphere