JAMB - Chemistry (2018 - No. 42)
In the laboratory preparation of oxygen, the gas cannot be collected by downward displacement of air because
the density of oxygen is greater than that of air
the density of air is nearly the same as that of oxygen
oxygen is a component of air
air is an impure substance
Uitleg
Oxygen is collected in downward displacement of water because:-
- Oxygen is only slightly soluble in water. Therefore, it can be collected over water without the fear of excessive dilution.
- Oxygen is slightly heavier than air, so it cannot be collected over air.