The fully hydrated form of sodium sulfate is the decahydrate,Na₂SO₄⋅10H₂O.This compound dehydrates (loses some waters of hydration)when heated.A sample of partially dehydrated sodium sulfate was found to have a molar mass of 232 g/mol.How many water molecules are found per formula unit in in this sample? (Determine n in Na₂SO₄⋅ nH₂O).

Question

Quizplus · Accepted Answer

The molar mass of Na2SO4 is 142 g/mol. The molar mass of H2O is 18 g/mol. Therefore, the molar mass of Na2SO4⋅10H2O is 142 + 10(18) = 322 g/mol. The molar mass of the partially dehydrated sample is 232 g/mol. Therefore, the number of water molecules per formula unit is (322 - 232) / 18 = 5.

The Fully Hydrated Form of Sodium Sulfate Is the Decahydrate,Na2SO4⋅10H2O

The Fully Hydrated Form of Sodium Sulfate Is the Decahydrate,Na₂SO₄⋅10H₂O