The fully hydrated form of sodium sulfate is the decahydrate,Na₂SO₄

Question

The fully hydrated form of sodium sulfate is the decahydrate,Na₂SO₄ • 10H₂O.When heated the hydrated salt loses water.How many water molecules are found per formula unit in a partially dehydrated sample of sodium sulfate with a formula mass of 197 amu (i.e.find n for Na₂SO₄ • nH₂O)? A)3 waters. B)5 waters. C)7 waters. D)9 waters. E)4 waters.

Quizplus · Accepted Answer

The formula mass of Na2SO4 is 142 amu, and the formula mass of H2O is 18 amu. Therefore, the formula mass of Na2SO4 • nH2O is 142 + 18n amu. If the formula mass of the partially dehydrated sample is 197 amu, then n = (197 - 142) / 18 = 3. Therefore, the partially dehydrated sample has the formula Na2SO4 • 3H2O.

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