Question

What is the number of moles and total number of atoms respectively present in 5.6 cm³ of ammonia gas at STP?

Options

• 1.505 mol and 6.022 × 10²⁰ atoms

• 2.05 mol and 1.50 × 10²⁰ atoms

• 2.50 × 10^-4 mol and 6.022 × 10²⁰ atoms

• 2.50 × 10^-3 mol and 1.5 × 10²⁰ atoms

Answer 1

2.50 × 10^-4 mol and 6.022 × 10²⁰ atoms

Explanation:

Vol. of NH₃ gas at STP = 5.6 cm³ = 5.6 × 10^-3 dm³

Now 22.4 dm₃ of NH₃ = 1 mole of NH₃ at STP

∴ 5.6 × 10^-3 dm³ of NH₃ = `(5.6 xx 10^-3)/22.4` = 2.5 × 10^-4 mol of NH₃

Now, No. of atoms = 2.5 × 10^-4 × 6.022 × 10²³ × 4 = 6.022 × 10²⁰ atoms