What is formed when an acid reacts with a base?

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?

Crystals of a substance changed their colour on heating in a closed test tube but regained it after sometime when they were allowed to cool down. Name the substance and write its formula and explain the phenomenon involved.

Who proposed the acid-base theory of ionization?

Which of the following relations is correct for a basic aqueous solution?

Which of the following substances enters our body when a red ant bites us?