Which metal does not react with acid?

Match the important chemicals given in Column $(A)$ with the chemical formulae given in Column $(B)$.

Column $(A)$	Column $(B)$
$(a)$ Plaster of Paris	$(i)$ $Ca(OH)_{2}$
$(b)$ Gypsum	$(ii)$ $CaSO_{4} \cdot 1/2 H_{2}O$
$(c)$ Bleaching Powder	$(iii)$ $CaSO_{4} \cdot 2H_{2}O$
$(d)$ Slaked Lime	$(iv)$ $CaOCl_{2}$

Write the chemical name and formula of the following:
$(a)$ Salt formed by the combination of a weak acid like carbonic acid and a strong base like sodium hydroxide.
$(b)$ Basic substance formed by the chlor-alkali process.
$(c)$ Substance added to cakes to make them fluffy.

Tooth enamel is the hardest substance in our body. Name the compound of which it is made up. At what $pH$ of the mouth does it get corroded? State the role of bacteria present in the mouth. Suggest a method to prevent tooth decay.

Which of the following substances is an antacid?

Which gas is produced when a base reacts with a metal?