The $P^H$  of a base solution is 12.699. The amount of crystalline oxalic acid  required to react with 2 lit of this base solution is (assume oxalic acid dissociates completely)

$P^H=12.699;P^{OH}=1.301$

$\left[O{H}^{-}\right]=AL\left(-2+0.699\right)$

                   $=+0.05$ .

$\text{wt}\text{of}\text{oxalic}\text{acid}=N\times GEW\times V$

                                $=0.05\times 63\times 2$

                                $=6.3gr$