SS2: Chemistry Theory Questions – Air

Question 1

[a]  give the constituents of atmospheric air and indicate its approximate percentage composition.

Answer:

Nitrogen – 78%
Oxygen – 21%
CO2 – 0.03%
Water vapour – Variable
Noble gases – 1%
Impurities (H₂ S, SO₄ ) – Variable

[b] Give three reasons why air is classified as a mixture.

Answer:

– The constituents can be easily separated by physical methods
– The constituents of air still retain their individual properties
– The composition of air cannot be represented by a chemical formula like ‘Compound’.

[c] How would you demonstrate that rainwater contains dissolved air?

Answer:

By carrying out an experiment of burning phosphorous in air, using the collected rainwater. After burning out the oxygen, read the volume of the mixture of gases left.