Question

Howmanymoleculesofairarein1cm3ofthisroom?(25°C,1atm)

Answer 1

Ans :

density of air at 25^oC and 1 atm is 1.1839 kg/m³

So mass of 1 m³ of air = 1.1839 kg

Since the air has majorly two components : 79% N2 and 21% O2

Mass of N2 = (1.1839 x 79) / 100 = 0.935281 kg = 935.281 g

Mass of O2 = (1.1839 x 21) / 100 = 0.248619 kg = 248.619 g

Moles of N2 = 935.281 / 28.0134 = 33.39 mol

Moles of O2 = 248.619 / 15.999 = 15.54 mol

Total moles = 33.39 mol + 15.54 mol

= 48.93 mol

1 mol has 6.022 x 10²³ molecules

So number of molecules : 48.93 x 6.022 x 10²³

= 2.95 x 10²⁵ molecules of air