Question

The concentration of $F^{-}$ ion in a sample of $H_{2}O$ is 18 ppm. What is the mass of $F^{-}$ ion present in 500 mL of water? (given density of water is $1.00{\text{g/cm}}^3$)

• A. 9 mg
• B. 8 mg
• C. 6 mg
• D. 18 mg

Answer 1

The correct option is A 9 mg

As density of water = 1 g/mL , using
$\text{Density}=\frac{\text{mass}}{\text{volume}}$
We get mass of water = $1\text{g/mL}\times 500\text{mL}=500\text{g}$
Now, Using
$\text{ppm}=\frac{\text{mass of solute (g)}}{\text{mass of solution(g)}}\times {10}^{6}18=\frac{\text{mass of solute}}{500}\times {10}^6$
Mass of solute $=\frac{500\times 18}{{10}^6}\text{g}=\frac{9000}{{10}^6}\text{g}$
$=\frac{9000}{{10}^6}\times {10}^3$ mg = 9 mg