Match the effect of addition of 0.1 M NaOH to 0.1 M, 50 mL H₃ PO₄ Ka₁, Ka₂, Ka₃ are the I, II, III ionization constant of H₃PO₄ respectively.

	Column-I (Vol. of NaOH added)		Column-II (pH of resultant solution)
A)	150 mL of NaOH	P)	$\mathrm{pH}={\mathrm{p}}^{k_{a_2}}$
B)	75 mL of NaOH	Q)	$\mathrm{pH}={\mathrm{p}}^{K_{a_1}}$
C)	25 mL of NaOH	R)	$\mathrm{pH}=7+\left[\frac{p^{K_{a_3}}+\log \mathrm{c}}{2}\right]$
D)	100 mL of NaOH	S)	$\mathrm{pH}=\frac{{\mathrm{p}}_{{\mathrm{k}}_{{\mathrm{a}}_2}}+{\mathrm{p}}_{{\mathrm{k}}_{{\mathrm{a}}_3}}}{2}$

	A	B	C	D
1.	T	P	Q,R,S	R
2.	P,Q,R,S	Q	P,Q,R,S	Q
3.	P	P	Q	S
4.	R	P	Q	S

$\begin{array}{l}{\mathrm{H}}_3{\mathrm{PO}}_4 + \mathrm{NaOH}⟶{\mathrm{NaH}}_2{\mathrm{PO}}_4+{\mathrm{H}}_2\mathrm{O}\\ 0.1\times 50 0.1\times 25\\ 5\mathrm{m} \mathrm{mole} 2.5\mathrm{m} \mathrm{mole} 0\\ \begin{array}{lll}2.5& -& 2.5\mathrm{mmole}\end{array}\\ 2.5\mathrm{mmole}\end{array}$
$\mathrm{pH}={\mathrm{p}}^{{\mathrm{Ka}}_1}$
Further addition of 25ml NaOH, only NaH₂PO₄ (5 m moles) will be formed

Further addition of 25 ml NaOH (Total 75 ml),
$\begin{array}{llc}{\mathrm{NaH}}_2{\mathrm{PO}}_4+\mathrm{NaOH}⟶{\mathrm{Na}}_2{\mathrm{HPO}}_4+{\mathrm{H}}_2\mathrm{O}& & \\ 5\mathrm{m} \mathrm{moles} & 2.5 \mathrm{moles} & 0\\ 2.5& -& \\ 2.5 \mathrm{m}\mathrm{moles} & 2.5\mathrm{m} \mathrm{moles} & \\ \therefore \mathrm{pH}={\mathrm{p}}^{{\mathrm{Ka}}_2}& & \end{array}$
Further addition of 25 ml NaOH, only Na₂ HPO₄ (5 m moles) will be formed
$\mathrm{pH}=\frac{{\mathrm{p}}^{{\mathrm{Ka}}_2}+{\mathrm{P}}^{{\mathrm{Ka}}_3}}{2}$
Further addition of 25 ml (Total 125 ml)
$\begin{array}{l}{\mathrm{Na}}_2{\mathrm{HPO}}_4+\mathrm{NaOH}⟶{\mathrm{Na}}_3{\mathrm{PO}}_4+{\mathrm{H}}_2\mathrm{O}\\ 5\mathrm{m} \mathrm{moles} 2.5\mathrm{mmoles}0\\ 2.5\\ \mathrm{ 2.5}\mathrm{m} \mathrm{moles} -2.5\mathrm{mmoles}\\ \therefore \mathrm{pH}={\mathrm{p}}^{{\mathrm{Ka}}_3}\end{array}$
Further addition of 25 m l (Total 150 m l Na₃PO₄ salt will be formed
$\mathrm{pH}=7+\frac{{\mathrm{p}}^{{\mathrm{Ka}}_3}}{2}+\frac{1}{2}\log \mathrm{C}$