When 5.20 g of salt is added to 5000 g of water, what is the concentration in parts per million (ppm)?

Hello!

Parts-per-million notation (ppm) is used for expressing small dimensionless quantities, usually ratios of mass to mass, volume to volume and so on.

In our problem, there are `5.20 g` of salt and `5000 g ` of water. Probably the ratio of mass to mass is required, although we can find densities of salt and water and calculate the volume to volume ratio, too.

The ratio `(5.20 g) / (5000 g)` is equal to `0.00104` (dimensionless). In other words, there are `0.00104` parts of salt for one part of water. Therefore there are

`1,000,000 * 0.00104 = 1040`

parts of salt for one million parts of water.

And this is the answer: the mass concentration is 1040 ppm. It may be expressed as 1040 ppm g/g also to avoid the confusion between masses and volumes.