Answer:
Step-by-step explanation:
First of all, 1 mol of Sodium Sulphide has molecular mass of
S = 32
Na2 = 2*23 = 46
The formula of NaS is actually Na2S. It's molecular mass = 78
How many grams of Na2S are present
Grams present = 240 - 162 = 78 which is exactly 1 mol.
The remainder is water.
The molecular mass of water = 2 + 16 = 18
162 grams of water = 162/18 = 9 mols of water.
So the correct formula is Na2S*9H20