State what happens when zinc granules are heated with sodium hydroxide solution. Write the balanced equation for this reaction. Name the main product formed in this reaction.

Which of the following contains oxalic acid?

Give three practical applications of neutralisation reaction.

$(a)$ Tooth enamel is one of the hardest substances in our body. Explain the changes in $pH$ of the mouth that indicate tooth decay. How does toothpaste help in preventing it?
$(b)$ What is the nature of the salt if the $pH$ of its solution is greater than $7$? Name the acid and base that would be used to prepare the following salts:
$(i)$ Potassium sulphate.
$(ii)$ Ammonium chloride.

Mention the range of $pH$ value for identification of a base.

$(i)$ What is meant by the term hydrated salt?
$(ii)$ Give two examples of hydrated salts that are white in color and state their chemical formulas.