Question

$\text{100}\,\text{c}{{\text{m}}^{\text{3}}}$ of $\text{0}\text{.1 M HCl}$ and $\text{100}\,\text{c}{{\text{m}}^{\text{3}}}$ of 0.1 M $\text{NaOH}$ solutions are mixed in a calorimeter. If the heat liberated is "Q" kcal, the heat of neutralisation $\text{( }\\!\\!\Delta\\!\\!\text{ H)}$ (in kcal) of $\text{HCl(aq)}$ and $\text{NaOH(aq)}$ is

• A. $-10Q$
• B. $-100Q$
• C. $-1000Q$
• D. $Q$

Answer 1

Answer: (B)

$-100Q$

Answer 2

Number of moles of $\text{HCl}=100\times 0.1=10$ Number of moles of $\text{NaOH =100}\times \text{0}\text{.1=10}$ $NaOH+HCl\xrightarrow{{}}NaCl+{{H}_{2}}O$ $\because$ when 1 mole of $\text{NaOH}$ is neutralised by mole of $\text{HCl,}$ Then, the heat liberated is = Q kcal or $\Delta H=-Q\,\text{kcal}$ $\therefore$ 10 moles of $\text{NaOH}$ are neutralised by 10 moles of $\text{HCl,}$ Heat liberated, $\Delta H=-10\times 10\times Q\,\text{kcal}$ $=-100Q\,\text{kcal}$