Question

If a sample of water contains $30$ ppm of $MgS{O}_4$, then its hardness is :

• A. $25$ ppm
• B. $20$ ppm
• C. $30$ ppm
• D. $150$ ppm

Answer 1

The correct option is A $25$ ppm

Molecular weight of $Mg{SO}_4$ $=120$ gms.
$120$ gms of $Mg{SO}_4$ has hardness $=100$ ppm.
$30$ ppm of $Mg{SO}_4$ has hardness $=\frac{100}{120}\times 30=25$ ppm.