Question

In aq. $so{l}^n$ oxalic acid exist as dihydrate $\left(\underset{\underset{COOH}{|}}{COOH\cdot 2H_{2}O}\right)$. If $6.3gm$ oxalic acid dissolve in $3L$ water. Calculate $PH$ of $so{l}^n$.

Answer 1

$(CCOH{)}_2.2H_{2}O\to$ Oxalic Acid.

Molecular mass of oxalic acid $=(12+16+16+1)\times 2+2\times 18$

$=126gm$

Mass of oxdic acid $=6.3gm$

No. of mole of oxdic acid $=\frac{6.3}{126}$

$=5\times {10}^{-2}$

Molarity = $\frac{5\times {10}^{-2}}{3L}=\frac{5}{3}\times {10}^{-2}M$

$\left[H^{+}\right]=2\times \frac{5}{3}\times {10}^{-2}=\frac{0.5}{3}$

$H_2{C}_2{O}_4\to 2H^{+}+C_2{O}_4^{2-}$

$pH=-\log \left[H^{+}\right]=-\log \frac{0.5}{3}$

$=-\log 0.5+\log 3=0.78$