25.2 gm of a mixture of `NaHCO_(3)` and `Na_(2)CO_(3)` is heated strongly, 0.66 gm of `CO_(2)` gas is evolved then the % mass of `Na_(2) CO_(3)` present in original mixture is -

Options

A. 0.1
B. 0.2
C. 0.45
D. 0.9

Answer

D

Explanation

`2NaHCO_(3) overset(Delta)(rarr) Na_(2)CO_(3) + H_(2)O + CO_(2)`
`n_(CO_(2)) = (0.66)/(44) = (3)/(200)`
`n_(NaHCO_(3)) = n_(CO_(2)) xx 2 = (3)/(200) xx 2 = 0.03`
`2NaHCO_(3) rarr Na_(2)CO_(3) + CO_(2) + H_(2)O`
`0.03` mole `n = (0.03)/(2)` mole
Mass `= 0.03 xx 84 = 2.52gm (NaHCO_(3))`
`%` by mass of `NaHCO_(3) = 10%` & `Na_(2)CO_(3) = 90%`