Question
The amount of heat evolved when $$0.50\,mole$$ of $$HCl$$ is mixed with $$0.30\,mole$$ of $$NaOH$$ solution is
A.
57.1$$\,kJ$$
B.
28.55$$\,kJ$$
C.
11.42$$\,kJ$$
D.
17.13$$\,kJ$$
Answer :
17.13$$\,kJ$$
Solution :
$$\eqalign{
& 0.50\,mol\,\,{\text{of}}\,\,HCl \equiv 0.50\,mol\,\,{\text{of}}\,\,{H^ + } \cr
& 0.30\,mol\,\,{\text{of}}\,\,NaOH \equiv 0.30\,mol\,\,{\text{of}}\,\,O{H^ - } \cr
& {H^ + } + O{H^ - } \to {H_2}O{\text{(Neutralisation)}} \cr
& 0.30\,mol\,\,{\text{of}}\,\,HCl \equiv 0.30\,mol\,\,{\text{of}}\,\,{H^ + } \cr
& {\text{or}}\,\,0.30\,mol\,\,{\text{of}}\,\,{H^ + } \equiv 0.30\,mol\,\,{\text{of}}\,\,O{H^ - } \cr
& {\text{Heat}}\,\,{\text{evolved with}}\,\,{\text{1}}\,{\text{mol}}\,\,{H^ + } = 57.1\,kJ \cr} $$
$${\text{Heat evolved with}}\,\,0.30\,mol\,\,{H^ + }$$ $$ = 57.1 \times 0.30 = 17.13\,kJ$$