Question

Explian why air is a mixture and not a compound?

Answer 1

Air is a mixture because: 

1. its composition varies because compoumds are always formed by mixing elements in definite proportions (which doesnt apply in case of air).
2. its constituents can be separated easily by "Fractional Distillation". 
3. No chemical reaction takes place when air is formed by mixing its constituents 
4. it has the properties of its constituent gases.