Question

A sample of drinking water was found to be severely contaminated with $CC{l}_4$, which is supposed to be carcinogenic in nature. The level of contamination was $20ppm$ (by mass). Calculate the mass percentage of $CC{l}_4$.

• A. $1.5\times {10}^{-3}\%$
• B. $1.5\times {10}^{-4}\%$
• C. $0.005\%$
• D. $0.002\%$

Answer 1

The correct option is D $0.002\%$

We know that:
$\text{part per million}=\frac{\text{mass of solute}}{\text{mass of solution}}\times {10}^6$
$\frac{\text{mass of solute}}{\text{mass of solution}}=\left(\text{parts per million}\right)\times {10}^{-6}$
$\text{mass percentage}=\frac{\text{mass of solute}}{\left(\text{mass of solution}\right)}\times {10}^2$
$\text{Mass percentage}=\left(\text{parts per million}\right)/{10}^4=2\times {10}^{-3}\%$