Question

What will be the final temperature attained if all the heat released in neutralization of $1Lof0.2M$ $N{H}_{4}OH$ with 2 L of $0.1MHCl$ increases the temperature of the final solution having density 0.95 gm/ml and specific heat capacity $=\frac{1}{3}J/g{m}^{0}C,$ if original temperature was ${27}^{0}C.$ Assume weak base to be completely unionized.

• A. ${310}^o$C
• B. $300K$
• C. $310K$
• D. $290K$

Answer 1

Answer: (C)

$310K$

$N{H}_{4}OH+HCl\stackrel{\Delta H_{reaction}}{\to }N{H}_{4}Cl+H_{2}O$
$N{H}_4^{+}+O{H}^{-}+H^{+}+C{l}^{-}\stackrel{\Delta H_{neutralisation}}{\to }N{H}_4^{+}+C{l}^{-}+H_{2}O$
$\Delta H_{reaction}=\Delta H_{ionisationofWB}+\Delta H_{neutralisation}$
$\Delta H_{reaction}=(+10-57.5)kJ$ unit extent of reaction $=-47.5kJ$
mole of $N{H}_{4}OH=0.2$
mole of $HCl=0.2$ No limiting reagent
Released heat $=0.2\times 47.5kJ=9.5kJ$

$Q_P=ms\Delta T$
$9.5\times 1000J=3000ml\times 0.95gm/ml\times \frac{1}{3}J/gm.K\times \Delta T$
$\Delta T=10$
$T_2=310K$