Concentration of Solutions
Percent by Mass
Problem 3. Dimercaprol, a compound used as an antidote for mercury or arsenic poisoning, is prepared by mixing 100 mg of dimercaprol with 700 mg of peanut oil. What is the percent by mass of dimercaprol in this solution?
Answer
1. Known: mass of dimercaprol = 100 mg; mass of peanut oil = 700 mg
2. Unknown: % dimercaprol (m/m)
3. Process: Use the equation:
\[
\begin{aligned}
\%\, \text{mass}
&=
\frac{
\text{mass of dimercaprol}
}{
\text{mass of dimercaprol} + \text{mass of peanut oil}
}
\times 100
\end{aligned}
\]
mass of dimercaprol = 100 mg; mass of peanut oil = 700 mg
mass of dimercaprol + mass of peanut oil = 800 mg
Therefore:
\[
\begin{aligned}
\text{dimercaprol}\,(m/m)
&=
\frac{100\,\text{mg}}{800\,\text{mg}} \times 100
\end{aligned}
\]
4. Answer: The solution contains 12.5% dimercaprol by mass.
