Question

Which of the following has maximum number of atoms?

Options

• 18g of H₂O

• 18g of O₂

• 18g of CO₂

• 18g of CH₄

Answer 1

18g of CH₄

`("Mass substance" xx ("Number of atoms in the molecule") xx "N"_"A")/"Molar mass"`

18 g of O₂ = 1 mole = 1 × 6.022 × 10²³

= 3 × 6.022 × 10²³ atoms = 1.8066 × 10²⁴ atoms

18 g of O₂  = `(18 xx 2)/32 xx 6.022 xx 10^23`

= 6.77 × 10²³ atoms

18 g of CO₂  = `(18 xx 3)/44 xx 6.022 xx 10^23`

= 7.39 × 10²³ atoms

18 g of CH₄ = `(18 xx 5)/16 xx 6.022 xx 10^23`

= 3.38 × 10²⁴ atoms