Which of the following is a mixture ?
Salt, Air, Water, Alum, Sugar
Answer: Air
Two matters do not combine with chemically called mixture.
Air is the mixture of gases like N2, O2, H2.
Alum is an addition compound (pure) (K2SO4. Al2(SO4)3.24H2O).
Salt is a compound, (pure). Chemical formula of common salt is NaCl.
Water is compound (pure) with chemical formula H2O.