Question

calculate the number of atoms in each of

1. 52 moles of argon

2. 52 g of helium

Answer 1

Argon and helium are monoatomic gases.

1. As we know 1 mole contain 6.022 × 10²³ particles.

Therefore 1 mole of Ar = 6.022 × 10²³ atoms.

⇒ 52 moles of Ar = 52 × 6.022 × 10²³ atoms

⇒ 52 moles of Ar = 331.26 × 10²³ atoms

Hence 52 moles of argon contain 3.31 × 10²⁵ atoms

2. Number of atoms in 52g of He.

As number of moles = given mass/ molar mass

Number of moles of He = 52/ 4 = 13

In 1 mole of Helium = 6.022 × 10²³ atoms.

∴ In 13 mole of Helium = 13 × 6.022 × 10²³ atoms.

Hence in 52g of helium there are 78.28 × 10²³ atoms.