Question

Calculate the mass percent of a NaCl solution in which 160 g of NaCl is dissolved in 3.13 L of water at 25 ∘C (density = 0.997 g/mL).Express your answer numerically.

Answer 1

The formula of mass percent is the following:

`\text{mass percent=}\frac{mass\text{ of solute}}{mass\text{ of solution}}`

where mass of solute correspond to the mass of NaCl and mass of solution correspond to the sum of NaCl and water mass.

We need to find the mass of water using its volume and density:

`\text{mass of water=}\frac{\text{density}}{\text{volume}}=\frac{0.997\text{ g/mL}}{3130\text{ mL}}=0.997\text{ g water}`

And we replace it in the first formula like this:

`\text{mass percent=}(160)/(160+0.997)=0.9938`

We obtain the percent multiplying the result by 100, so the answer is 99.38%