Foundation
Chemistry Foundation
Preparation and Uses of Some Compounds
Atomic and Molecular Mass
Mole Concept and Calculation
Question
Calculate the formula unit mass of CaSO4.2H2O.
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Solution
Formula unit mass of CaSO4.2H2O
= (Number Calcium atoms x atomic mass of Calcium) + (Number Sulphur atoms x atomic mass of sulphur) + (Number Oxygen atoms x atomic mass of Oxygen) + (Number Water molecules x Molecular mass of water molecule)
= (1 × 40) + (1 × 32) + (4 × 16) + (2 × 18)
= 40 + 32 + 64 + 36
= 172
Formula unit mass of gypsum = 172