Question

which of the following material fall in category of pure substance ? ice ,milk, hydrochloric acid,calcium oxide ,mercury and air​

Answer 1

mercury falls into category of pure substance.

If the air is made from any pure gas like nitrogen, oxygen, Argon, Hydrogen or Helium then it will also be a pure substance.

Answer 2

Following substance from the above mentioned list are pure substance :

$\sf\red{★Ice}$

$\sf\red{★Hydrochloric\:acid}$

$\sf\red{★Calcium\:oxide}$

$\sf\red{★Mercury}$