A 0.05 L sample of 0.2 M aqueous hydrochloric acid is added to 0.05 L of 0.2 M aqueous ammonia in a calorimeter. Heat capacity of entire calorimeter system is 480 J/K. The temperature increase is 1.09 K. Calculate `Delta_(r )H^(@)` in kJ/mol for the following reaction :
`HCl(aq.)+NH_(3)(aq.)rarrNH_(4)Cl(aq.)`

Options

A. `-52.3`
B. `-61.1`
C. `-55.8`
D. `-58.2`

Answer

A

Explanation

m mole of acid `= 0.05 xx 0.2 = 0.01`
`Delta_(r)H^(@) = (480 xx 1.09)/(0.01 xx 1000) = -52.32 kJ//mol`