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. 10 ppm
B. 5 ppm
C. 8 ppm
D. 6 ppm

Answer 1

Correct Answer - A
Mw of washing soda`=286 mW of CaCO_(3)=100g mol^(-1)`
`CaSO_(4)+Na_(2)CO_(3)toCaCO_(3)+Na_(2)SO_(4)`
`0.0286g Na_(2)CO_(3).10H_(2)O=(0.0286)/((286)/(2))xx10^(3)=0.2mEq`
`0.2 m" Eq of "Na_(2)CO_(3)=(0.2)/(2)m" mol of "CaCO_(3)` in 1L
`=(0.1xx10^(-3))xx100g` in `10^(3) mL`
`=0.01 g` in `10^(3)mL`
`ppm=(0.01xx10^(6))/(10^(3))=10ppm`