Why is nitric added to sodium extract before adding silver nitrate for testing halogens?

Why Chemicals are added to food?

While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

What is observed when sodium chloride is added to a colloidal solution of Ferric hydroxide?

In cold countries, ethylene glycol is added to water in radiators of cars during winters. Why?

Why is that an orange solution of K_2Cr_2O_7 turns yellow on adding NaOH to it?

Why does a needle float on clear water, but sinks when some detergent is added to water?

Decrease in vapour pressure of water by adding 5 mol sucrose or 5 mol urea to one kg of water is same why?