Answer:
1.293 kg/m³
Explanation:
Density: this can be defined as the ratio of the mass of a body and its volume.
The S.I unit of density is kg/m³
D = m/v............................ Equation 1
D = density of air, m = mass of air, v = volume of air.
<em>Note: Since the air is made up of nitrogen, oxygen and argon. the mass and volume of air will be the sum of the mass and sum of the volume of nitrogen, oxygen, and argon respectively.</em>
(i) Mass of one mole of N₂ = 28 g
Therefore, mass of 0.78 mole of N₂ = 28×0.78 = 21.84 g.
(ii) Mass of one mole of O₂ = 32 g
Therefore, mass of 0.21 mole of O₂ = 32×0.21 = 6.72 g
(iii) Mass of one mole of Ar = 40 g
Therefore mass of 0.01 mole of Ar = 0.01×40 = 0.4 g
m = 21.84 + 6.72 + 0.4 = 28.96 g
Also Note: One mole of every gas at standard temperature and pressure = 22.4 dm³
Therefore,
(i) volume of 0.78 mole of N₂ = 22.4×0.78 = 17.47 dm³
(ii) volume of 0.21 mole of O₂ = 0.21×22.4 = 4.704 dm³
(iii) volume of 0.01 mole of Ar = 0.01×22.4 = 0.224 dm³
Therefore,
v = 17.47+4.704+0.224
v = 22.398 dm³
Substituting the value of v and m into equation 1
D = 28.96/22.398
D = 1.293 g/dm³
D = 1.293 kg/m³
