Question

A given sample of sulphur contains 0.25 mol of sulphur molecules. The number of
moles of sulphur atoms, number of sulphur molecules and number of sulphur atoms present in the given sample are respectively
(A) 6.023 x 10^23, 3 and 3.2 x 10^23
(B) 2,3.2 x 10^23 and 6.02 x 10^23
(C) 2, 1.5 x 10^23 and 1.2 x 10^24
(D) 1.2 x 10^24, 3.2 x 10^23 and 2
(E) None of these
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Answer 1

A given sample of sulphur contains 0.25 mol of sulphur molecules.

• Mole is just a basic unit to measure large number of atomic particles. it is dimensionless quantity and 1 mole of any substance is denoted by Avogadro's number which is equal to 6.023 × 10²³.

• 1 mole of any atom means 6.023 × 10²³ atoms

The sample of sulphur contains 0.25 mol of sulphur molecules.

we know, 1 molecule of sulphur contains eight sulphur atoms.

so, 0.25 mol of sulphur molecules = 8 × 0.25 = 2 moles of sulphur atoms.

Therefore the number of moles of sulphur atoms is 2.

number of sulphur molecules = no of moles of sulphur molecules × Avogadro's number

= 0.25 × 6.023 × 10²³

≈ 1.5 × 10²³

Therefore the number of sulphur molecules is 1.5 × 10²³.

number of sulphur atoms = no of moles of sulphur atoms × Avogadro's number

= 2 × 6.023 × 10²³

≈ 1.2 × 10²⁴

Therefore the number of sulphur atoms is 1.2 × 10²⁴

Hence the correct option is (C).