Question

What mass of ethane (CH 3CH 3) is contained in 50.0 mL of a 13.9% by mass solution of ethane in hexane? The density of the solution is 0.611 g/mL.8.49 g4.25 g2.35 g6.95 g11.8 g

Answer 1

Mass percent is given by:

`\begin{gathered} mass\%=\frac{mass\text{ }solute}{mass\text{ }of\text{ }solution}*100 \\ \end{gathered}`

We need to determine the mass of the solution by using the density:

`\begin{gathered} \rho=(mass)/(volume) \\ \rho:density \\ \\ 0.611gmL^(-1)=(mass)/(50.0mL) \\ mass=50.0mL*0.611gmL^(-1) \\ mass(solution)=30.55g \\ \end{gathered}`

We can plug this value into the mass percent formula to determine the mass of the solute:

`\begin{gathered} mass\%=\frac{mass\text{ }solute}{mass\text{ }of\text{ }solution}*100 \\ \\ 0.139=\frac{mass\text{ }solute}{30.55g} \\ mass\text{ }solute=0.139*30.55g \\ mass\text{ }solute=4.25g \end{gathered}`

Answer: Mass of solute is 4.25g.