Question

To a 10mL, 1M aqueous solution of `Br_(2)`, excess of NaOH is added so that all `Br_(2)` is disproportionated to `Br^(-)` and `BrO_(3)^(-)`. The resulting solution is free from `Br^(-)`, by extraction and excess of `OH^(-)` neutralised by acidifying the solution. The resulting solution is suffcient to react with 2 g of impure `CaC_(2)O_(4)`(M= 128g/mol) sample. The % purity of oxalate sample is :
A. `85.3%`
B. `42.6%`
C. `63.75%`
D. `21.3%`

Answer 1

Correct Answer - A
`{:(3Br_(2)+6OH^(-)rarr,5Br^(-)+,BrO_(3)^(-)+3H_(2)O),(0,-1,+5):}`
`6H^(+) +BrO_(3)^(-) +3C_(2)O_(4)^(2-) rarr Br^(-) +6CO_(2)+3H_(2)O`
10m. Mole `Br_(2) rarr 10//3`m. mole of `BrO_(3)^(-)`
`rArr 10ml`. mol of `C_(2)O_(4)^(2-)`
% purity `=(10 xx 10^(-3) xx 128)/(1.5) = 100 = 85.3`