What happens when nitric acid is added to an egg shell?

Crystals of copper sulphate are heated in a test tube for some time.
$(a)$ What is the colour of copper sulphate crystals:
$(i)$ before heating, and $(ii)$ after heating?

Match the acids given in Column $(A)$ with their correct source given in Column $(B)$.

Column $(A)$	Column $(B)$
$(a)$ Lactic acid	$(i)$ Tomato
$(b)$ Acetic acid	$(ii)$ Lemon
$(c)$ Citric acid	$(iii)$ Vinegar
$(d)$ Oxalic acid	$(iv)$ Curd

Write true or false for the following statements:
Care must be taken while mixing concentrated nitric acid or sulphuric acid with water. The water must always be added slowly to the acid with constant stirring.

Give three practical applications of neutralisation reaction.

How is an aqueous solution with $pH$ $12$ compared to an aqueous solution with $pH$ $9$?