Question

$50.0mL$ of $0.10MHCl$ is mixed with $50.0mL$of $0.10MNaOH$. The solution's temperature rises by ${0.6}^{o}C.$ Calculate the enthalpy of neutralization per mole of $HCl$.
Given : density and specific heat of solution is $1gm{L}^{-1}$ and 4.2 $J{g}^{-1\circ }{C}^{-1}$

• A. $-50.4kJ/mol$
• B. $-54.4kJ/mol$
• C. $-57.7kJ/mol$
• D. $-63.2kJ/mol$

Answer 1

The correct option is A $-50.4kJ/mol$

Balanced chemical reaction :
$HCl+NaOH\to NaCl+H_{2}O$
Milimoles = Molarity $\times$ Volume of solution in $mL$
Milimoles of $HCl$ = $0.1\times 50=5mmol$
Milimoles of $NaOH$ = $0.1\times 50=5mmol$
Hence millimoles of acid neutralized = 5 mmol
Specific heat capacity is 4.2 $J{g}^{-1\circ }{C}^{-1}$
Heat released $\left(q\right)=ms△T=100\times 4.2\times 0.6=252$
Enthalpy of neutralization per mole of $HCl$ $△H=-252J\times \frac{1000}{5}=-50.4kJ/mol$