A 500 cm³ sample of swimming pool water contained 0.1 g of dissolved solids - Leaving Cert Chemistry - Question i - 2018

To convert grams to milligrams, we multiply by 1000:

$$0.1 ext{ g} = 0.1 imes 1000 = 100 ext{ mg}$$

The volume of the sample is 500 cm³, which is equivalent to 0.5 litres. Therefore, to find the concentration in mg per litre, we divide the mass of the dissolved solids by the volume of the sample in litres:

ext{Concentration} = rac{100 ext{ mg}}{0.5 ext{ L}} = 200 ext{ mg/L}