Question

Washing soda `(Na_(2)CO_(3).10H_(2)O)` is widely used in softening of hard waer. If 1 L of hard water requires 0.0286 g of washing soda, the hardness of `CaCO_(3)` in ppm is
A. 10ppm
B. 5 ppm
C. 8ppm
D. 6ppm

Answer 1

Correct Answer - A
(a) Mw of washing soda `= 286`,
`CaSO_(4) +Na_(2) CO_(3) rarr CaCO_(3)+Na_(2)SO_(4)`
m. moles of `Na_(2)CO_(3).10H_(2)O =m`. Moles of `CaCO_(3) =` m. moles of salt causing hardness
Hardness of `CaCO_(3) = (28.6)/(286) xx (100)/(1) = 10` ppm