Define the term Mole.
A gas cylinder contains 24 × 10^24 molecules of nitrogen gas. If Avogadro’s number is 6 × 10^23 and the relative atomic mass of nitrogen is 14, calculate :
(i) Mass of nitrogen gas in the cylinder.
(ii) Volume of nitrogen at STP in dm3

Mole — A mole is the amount of substance which contains the same number of units as the number of atoms in 12,000 g of carbon – 12 [₆C¹²]

(i) Gram molecular mass of N₂ = 2(14) = 28 g

6 × 10²³ molecules of N₂ weighs 28 g

∴ 24 × 10²⁴ molecules will weigh = 28\over 6 × 10^23 × 24 × 10²⁴ = 1120 g

(ii) 6 × 10²³ molecules of N₂ occupies 22.4 dm³

∴ 24 × 10²⁴ molecules of N₂ will occupy = 22.4\over 6 × 10^23 × 24 × 10²⁴

= 896 dm³

Hence, Mass of nitrogen gas = 1120 g and vol. occupied is 896 dm³