Question

The amount of energy released when $20mL$ of $0.5MNaOH$ are mixed with $100mL$ of $0.1MHCl$ is $xkJ$. The heat of neutralisation is : (in $kJmo{l}^{-1}$)

• A. $-100x$
• B. $-50x$
• C. $+100x$
• D. $+50x$

Answer 1

The correct option is A $-100x$

Find milliequivalents of $NaOH$ and $HCl$ and equate them.
Given, $20mL$ of $0.5MNaOH$
$100mL$ of $0.1MHCl$
Milliequivalents (or millimoles) of $NaOH=20\times 0.5=10$
Milliequivalents (or millimoles) of $HCl=100\times 0.1=10$
$\therefore 10$ milliequivalents on neutralisation given $=-xkJ$ heat
$\therefore 1g-eq$ (ie, $1000$ milliequivalents) will give
$=-x\times 100$
$=-100xkJheat$