`5gNa_(2)CO_(3)` and `Na_(2)SO_(4)`. This sample is dissolved and the volume made up to 250 mL, 25 mL 20 mL `0.1 M H_(2)SO_(4)` . Calculate the % of `Na_(2)SO_(4)` in the sample

Options

A. 42.4
B. 57.6
C. 36.2
D. None of these

Answer

B

Explanation

Only `Na_(2)CO_(3)` is reacted with
`Na_(2)CO_(3)+H_(2)SO_(4)toNa_(2)SO_(4)+H_(2)CO_(3)`
m-moles of `Na_(2)CO_(3)=m` =m-moles of `H_(2)SO_(4)`
`=20xx0.1=2`
m-moles of `Na_(2)CO_(3)` in 250 mL solution
`=(250)/(25)xx2=20`
wt. of `Na_(2)CO_(3)=20xx106xx10^(-3)=2.12g`
% of `=(2.12)/(5)xx100=42.4`
% of `Na_(2)SO_(4)=100-42.4=57.6`