A sample of hard water is found to contain 40 mg of `Ca^(2+)` ions per litre. The amount of washing shoda `(Na_(2)CO_(3))` required to soften `5*0`L of the sample would be

Options

A. `1*06 g`
B. `5*3 g`
C. `53 mg`
D. `530 mg`

Answer

D

Explanation

The equation is
`Ca^(2) + Na_(2)CO_(3) to CaCO_(3) + 2Na^(+)`
Total `Ca^(2+)` in 5 L of hard water `= 5xx40 = 200 mg`
Now from equation, 40 g `Ca^(2+)` required washing soda = 106 g
`:. 200 mg` of `Ca^(2+)` will require washing soda
`=(106)/(40)xx200xx10^(-3)g = 0.530 g` or `530 mg`