# Question #19ef4

##### 2 Answers

#### Answer:

#### Explanation:

You have

Percent concentration by mass is defined as the mass of solute, in your case ethane, divided by the *total mass of the solution*, and multiplied by

In order to be able to calculate the amount of ethane present in that much

To do that, use its density and volume

#rho = m/V => m = rho * V#

#m_"solution" = 0.611"g"/cancel("mL") * 50cancel("mL") = "30.55 g"#

You know that the mass of the solute accounts for

#"13.9%" = m_"ethane"/m_"solution" * 100% => m_"ethane" = ("13.9%" * m_"solution")/(100%)#

#m_"ethane" = (13.9cancel(%) * 30.55)/(100cancel(%)) = "4.246 g"#

Now, I'm going to give the answer rounded to two sig figs, even though you only gave one sig fig for the volume of the solution

#m_"ethane" = color(green)("4.2 g")#

4.2g

So:

So: