(a) Define gram molecular mass of a substance. How much is the gram molecular mass of oxygen?(b) If sulphur exists as S8 molecules, calculate the number of moles in 100 g of sulphur. (S = 32 u)

Academic Chemistry NCERT Class 9

(a) Gram molecular mass refers to the mass of a molecule in one mole of molecules of that substance. It is equal to the gram molecular weight of that element.

Oxygen exists as a diatomic molecule (O₂). Hence, the gram molecular mass of oxygen is 32 grams.

(b) Mass of sulphur = 100g (sulphur exists as S8 molecules)

Molecular mass of sulphur = (8 × 32) = 256g

Number of moles in 256g of sulphur = 1 mole

Number of moles in 100g of sulphur = 100/256 = 0.39 moles

Therefore, 100g of sulphur contains 0.39 moles of sulphur.

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Updated on: 10-Oct-2022

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