Rainwater contains carbonic acid. Rainwater will dissolve calcium carbonate. The natural water supply in The United States contains calcium.
Calculate the concentration, in mol/ dm^3, of the solution formed by dissolving 8 g of calcium carbonate in 500 cm^3 of rainwater. (Ca = 40, C =12, O = 16, H = 1 )
thanks in advance

Calculate the molar mass of CaCO3 and take out the number of moles
moles = mass / molar mass
           now divide  moles by litres (volume) to get the concentration