Question

Different samples of water contained each $100$ ppm of $CaC{l}_2,MgS{O}_4,CaS{O}_4$ and $MgC{l}_2$. Among them which will have greater hardness?

• A. $CaC{l}_2$
• B. $MgC{l}_2$
• C. $CaS{O}_4$
• D. $MgS{O}_4$

Answer 1

The correct option is B $MgC{l}_2$

$110$ gms of $Ca{Cl}_2$ has hardness $=100$ ppm
$100$ ppm of $Ca{Cl}_2$ has hardness = $\frac{100}{110}\times 100=90.9$ ppm
$120$ gms of $Mg{SO}_4$ has hardness $=100$ ppm
$100$ ppm of $Mg{SO}_4$ has hardness $=\frac{100}{120}\times 100=83.3$ ppm
$136$ gms of $Ca{SO}_4$ has hardness $=100$ ppm
$100$ ppm of $Ca{SO}_4$ has hardness = $\frac{100}{136}\times 100=73.5$ ppm
$94$ gms of $Mg{Cl}_2$ has hardness $=100$ ppm
$100$ ppm of $Mg{Cl}_2$ has hardness = $\frac{100}{94}\times 100=106.4$
Therefore, $Mg{Cl}_2$ has maximum hardness.