Distinguish betwe

OR

(i) Removing iron filings from the mixture by magnetic separation: Take the mixture in a petri dish and roll a bar magnet over it. Iron filings will get attached to the magnet and thus separate from the mixture.

Removing ammonium chloride by sublimation: Transfer the remaining mixture into a China dish and heat it. On heating, ammonium chloride sublimes and solidifies on cooling. The mixture contains a sand and sodium chloride left behind in the China dish.

Removing sand by filtration: Make a solution of sand and sodium chloride in water. Filter the solution. Sodium chloride will dissolve in water and sand is left as residue on the filter paper.

Evaporate the filtrate to dryness to get sodium chloride or by crystallisation.

(ii) (a) Chemical change.

(b) Acidic and basic solutions can be prepared by dissolving the products of the above process in water.

CaO + H2O → Ca(OH)2 (basic solution)

CO2 + H2O → H2CO3 (acidic solution)