Question

A gas cylinder contain 12 × 10²⁴ molecules of oxygen gas
If Avogadro's number is 6 × 10²³,
calculate :
(i) The mass of oxygen present in the cylinder.
(ii) The volume of oxygen at STP present in the Cylinder[O=16]

Answer 1

1 mole oxygen molecule = 6.022 x 10²³ molecules.
19.93 moles of Oxygen molecule = 12 x 10²⁴ molecules
Number moles of O₂ = `"Mass of O"_2/"Molar mass of CO"_2`
Mass of O₂ = 32 x 19.93 = 637.76g
(ii) 6.022 x 10²³ molecules occupies 22.4L
12 x 10²⁴ molecules occupies = `[12 xx 10^24 xx 22.4]/[6.022 xx 10^23]`
= 446.36L volume.