Question

Equal volumes of molar hydrochloric acid and sulphuric acid are neutralized by dilute $NaOH$ solution and $x$ $kcal$ and $y$ $kcal$ of heat are liberated respectively. Which of the following is true?

• A. $x=y$
• B. $x=\frac{y}{2}$
• C. $x=2y$
• D. None of these

Answer 1

Answer: (B)

$x=\frac{y}{2}$

Heat of neutralisation $=$ Heat of formation of water (1 mole)
$HCl+NaOH⟶NaCl+H_{2}O$;
or $\underset{1mol}{H^{+}}+\underset{1mol}{O{H}^{-}}⟶\underset{1mol}{H_{2}O}$;
$H_{2}S{O}_4+2NaOH\to {Na}_{2}S{O}_4+2H_{2}O$;
or $2H^{+}+2O{H}^{-}⟶2H_{2}O$;
$H^{+}+O{H}^{-}⟶H_{2}O$
$\Rightarrow \Delta H=\Delta H$
$\therefore x=\frac{y}{2}$