Help please! Density Equation.

Question

If you dissolve 615 g of salt in 34500 ml of water, what is the density of that solution of salty water? In this particular example, assume that the total volume doesn’t change when salt is added to water. You will need the mass of salt and the mass of water to find the mass of the solution of salty water. Don’t forget to show your working and include SI units.

Answer 1

Density = mass/volume

Let us first determine the mass:

We will add the mass of the water to the mass of the salt. But first we need to find the mass of the water.

Mass water: 34,500 ml x 1 g/ml = 34,500 g (assuming a density of H2O of 1.0 g/ml)

Mass salt: 615 g as given

Total mass = 34,500 g + 615 g = 35,115 g

Total volume = 34,500 ml (volume did not change when adding salt)

Density = mass/volume

Density = 35,115 g / 34,500 ml = 1.02 g/ml (to 3 significant figures)

SI units for density are kg/m³ so the answer will be 1.02 kg/m³ (to 3 significant figures)