`0.7 g " of " Na_(2)CO_(3).xH_(2)O` were dissolved in water and the volume was made to `100 mL, 20 mL` of this solution required `19.8 mL " of " N//10 HCl` for complete neutralization. The value of `x` is:

Options

A. 7
B. 3
C. 2
D. 5

Answer

C

Explanation

Number of milliequivalents of `Na_(2)CO_(3).xH_(2)O` in 20 mL
`=19.8xx(1)/(10)`
=1.98
`therefore` Number of milliequivalents in 100 mL `=1.98xx5=9.9`
`("Mass")/("Equivalent mass")xx1000=9.9`
`(0.7)/(M//2)xx1000=9.9`
M=141.40
(Molar mass of `Na_(2)CO_(3). xH_(2)O)`
106+18x=141.40
x=2