Question

The concentration of $B{r}^{-}$ ion in a sample of $H_{2}O$ is 36 ppm. What is the mass of $B{r}^{-}$ ion is present in 250.0 mL of water ? (given density of water is 1.00 g/$c{m}^3$)

• A. 2.0 mg
• B. 9.0 mg
• C. 12.0 mg
• D. 5.0 mg

Answer 1

The correct option is B 9.0 mg

As density of water = 1 g/mL , using
$Density=\frac{mass}{volume}$
We get mass of water = $1g/mL\times 250mL$
$=250g$
Now, Using
$ppm=\frac{\text{mass of solute (g)}}{massofsolution\left(g\right)}\times {10}^{6}36=\frac{\text{mass of solute}}{250}\times {10}^6$
Mass of solute $=\frac{250\times 36}{{10}^6}g=\frac{9000}{{10}^6}g$
$=\frac{9000}{{10}^6}\times {10}^3$ mg = 9 mg