6.2 g of a sample containing `NaHCO_(3)`, `NaHCO_(3)` and non -volatiale inert impurity on gentle heating loses 5% of its mass due to reaction `2NaHCO_(3)to Na_(2)CO_(3)+H_(2)O+CO_(2).` Residue is dissolved in water and formed 100 mL solution and its 10 mL portion requires 7.5 mL of 0.2 M aqueous solution of `BaCl_(2)` for complete precipitation of carbonates.
Determine mass (in gram) of `Na_(2)CO_(3)` in the original sample .

Answer

`1.06g`

Explanation

`Na_(2)CO_(3)+BaCl_(2)rarrBaCO_(3)darr+2NaCl`
`m`.moles
`7.5xx0.2`
Total `m`. moles `=15`
`2NaHCO_(3)rarrNa_(2)CO_(3)+H_(2)O+CO_(2)`
`?" "(n)/(2)" "(n)/(2)`
`wt.=9n+22n=31n=0.31`
`n=0.01`
`W_(Na_(2)CO_(3))=(19)/(1000)xx106=1.06gm`