Question

Calculate the mass of calcium ions present in 1L of hard water if the concentration of calcium ions is 40 ppm. (Assume
density of hard water to be 1g/cc)​

Answer 1

ANSWER

The density of water sample is 1.0 g/ml.

Thus, 1 L (or 1000 mL) of water sample weighs 1 kg (or 1000 g).

486 ppm corresponds to 486 g of calcium bicarbonate in 1000 g or 1000 L of water sample.

Thus, 1 L of water sample contains 0.486 g of calcium bicarbonate.

The molar mass of calcium bicarbonate is 162.11 g/mol.

The molarity of the solution =

Molar mass of calcium bicarbonate×Volume of water sample

Mass of calcium bicarbonate

=

162.11×1

0.486

=3.0×10

−3

M