Question

Estimate the total number of air molecules (Inclusive of oxygen, nitrogen, water vapour, and other constituents) in a room of capacity 25.0 m³at a temperature of 27 °C and 1 atm pressure.

Answer 1

From ideal gas law

PV = nRT

Here P = atm = 1. 013 × 10⁵ Pa.

V = Volume = 25 m³

T = Temperature = 27°C = 300k

n = no of moles of gas

R = Gas constat = 8. 314 J mol^-1 k^-1

= 0.01015 × 10⁵ =1015 mol

Since 1 mol ≅ 6. 023 × 10²³ molecules

N = 1015 mol ≅ 6.023 × 10²³ × 1015

N = 6.113 × 10²⁶ molecules.

∴ The total no of molecules in the given room is 6.113 × 10²⁶.