Question

calculate the number of calcium ions present in 0.68 grams of calcium sulphate?

Answer 1

Molar mass of CaSO4 = 136.14 g/mol

Moles of CaSO4 = 0.68 g/ 136.14 g/mol = 0.0049 mol

Moles of Ca2+ ion = 1x 0.0049 mol = 0.0049 mol

There are 6.022 x 10^23 molecules per mole. So, 0.0049 times Avagadro's number will give you the number of calcium ions in 0.68 g of calcium sulphate.

Therefore number of calcium ions in 0.68 g of CaSO4 = 0.0049 x 6.023x10^23 ions

= 2.95 x10^21 ions