Question

Calculate the percent by mass of the solute in each of the following aqueous solutions: (a) 5.50 g of NaBr in 78.2 g of solution, (b) 31.0 g of KCl in 152 g of water, (c) 4.5 g of toluene in 29 g of benzene.

Answer 1

Answer:

For a: The mass percent of NaBr is 7.03 %

For b: The mass percent of KCl is 16.94 %

For c: The mass percent of toluene is 13.43 %

Explanation:

To calculate the mass percentage of solute in solution, we use the equation:

$\text{Mass percent of solute}=\frac{\text{Mass of solute}}{\text{Mass of solution}}\times 100$         .......(1)

• For a:

We are given:

Mass of NaBr (Solute) = 5.50 g

Mass of solution = 78.2 g

Putting values in equation 1, we get:

$\text{Mass percent of NaBr}=\frac{5.50g}{78.2g}\times 100\\\\\text{Mass percent of NaBr}=7.03\%$

Hence, the mass percent of NaBr is 7.03 %

• For b:

We are given:

Mass of KCl (Solute) = 31.0 g

Mass of water (solvent) = 152 g

Mass of solution = (31.0 + 152) g = 183 g

Putting values in equation 1, we get:

$\text{Mass percent of KCl}=\frac{31.0g}{183g}\times 100\\\\\text{Mass percent of KCl}=16.94\%$

Hence, the mass percent of KCl is 16.94 %

• For c:

We are given:

Mass of toluene (Solute) = 4.5 g

Mass of benzene (solvent) = 29 g

Mass of solution = (4.5 + 29) g = 33.5 g

Putting values in equation 1, we get:

$\text{Mass percent of toluene}=\frac{4.5g}{33.5g}\times 100\\\\\text{Mass percent of toluene}=13.43\%$

Hence, the mass percent of toluene is 13.43 %