Question

If $HA+NaOH\to NaA+H_{2}O,\Delta H=-12$ kcal

and $HB+NaOH\to NaB+H_{2}O,\Delta H=-11$ kcal

then equimolar solution of which acid has higher pH

• A. HA
• B. HB
• C. both have same pH
• D. information insufficient

Answer 1

The correct option is B HB

$HA+NaOH\to NaA+H_{2}O\Delta H=-12$ kcal
$HB+NaOH\to NaB+H_{2}O\Delta H=-11$ kcal

As HB has a lower neutralisation energy, so it will require more energy to dissoicate in water. As a result, it will have less hydrogen ions in water.

So it will have a higher $pH$ as

$pH=-log\left[H^{+}\right]$