Question

A sample of water contains $1\times {10}^{-3}$ moles of per $10$ kg of water. Calculate the degree of hardness of water.

• A. $50$ ppm
• B. $500$ ppm
• C. $100$ ppm
• D. $10$ ppm

Answer 1

The correct option is D $10$ ppm

${10}^4$ gms of water contain ${10}^{-3}$ moles
${10}^6$ gms of water contain $\frac{{10}^{-3}}{{10}^4}\times {10}^6$ = $0.1$ mole.
$1$ mole has degree of hardness $=100$ ppm
$0.1$ mole has degree of hardness $=100\times 0.1=10$ ppm