The exact volumes of 1MNaOH solution required to neutralise 50mL of...

${H}_{3}{PO}_{3} + 2NaOH \to {Na}_{2}{HPO}_{3} + 2{H}_{2}O$

$\begin{cases}50ml & 1M\end{cases}$

$1MV = ?$

$⇒ \dfrac{{n}_{NaoH}}{{n}_{{H}_{3}{PO}_{3}}} = \dfrac{2}{1}$

$⇒ \dfrac{1 \times V}{50 \times 1} = \dfrac{2}{1} ⇒ {V}_{NaOH} = 100ml$

${H}_{3}{PO}_{2} + NaOH \to {NaH}_{2}{PO}_{3} + {H}_{2}O$

$2M1M$

$100mLV = ?$

$⇒ \dfrac{{n}_{NaoH}}{{n}_{{H}_{3}{PO}_{3}}} = \dfrac{1}{1} ⇒ \dfrac{1 \times V}{2 \times 100} = \dfrac{1}{1} ⇒ {V}_{NaOH} = 200ml$