\(\Delta\)\(n_g\) \(= 2 - 3 = -1\)
\(\Delta E = -670.48 \,kcal\)
\(\Delta H = \Delta U + \Delta n_g RT\)
\(\Delta H = -670.48 - 1× 2 × 10^{-3}×298 = -671.08 \,kcal\)
$(i)$ $NH_3$ $_{(g)} + aq$ $\rightarrow$ $NH_3$ $_{(aq)}$, $\Delta H$ $= -8.4 \,Kcal.$
$(ii)$ $HCl_{(g)} + aq$ $\rightarrow$ $HCl{(aq)}$, $\Delta H =$ ${-1}7.3\, Kcal.$
$(iii)$ $NH_3$ $_{(aq)} + HCl_{(aq)}$ $\rightarrow$ $NH_4Cl $ $_{(aq)}$, $\Delta H = -12.5\, Kcal$.
$(iv)$ $NH_4Cl$ $_{(s)} + aq$ $\rightarrow$ $NH_4Cl$ $_{(aq)}$, $\Delta H = +3.9 \,Kcal.$
($\Delta H$ અને $\Delta S$ તાપમાન સાથે બદલાતા નથી તેમ ધારો)