Question

How to separate the mixture of sand salt and ammonium chloride

Answer 1

You can separate them by mixing them in water then sent will sediment while salt and ammonium will be mixed in water.

After that heat the water you will get salt deposited and Nh3 vapours.

Answer 2

Here's your answer :

You can separate the mixture by just heating it . Ammonium chloride will undergo the process of sublimation and will get evaporate. We can get it back by condensing the vapours.
Also sand salt remains in the beaker in which you heat the mixture.