According to the Bronsted-Lowry acid-base theory,the substance which accepts a proton $(H^+)$ from another substance is called ...........

Why do acids not show acidic behaviour in the absence of water?

Give reasons for the following:
$(a)$ Dry $HCl$ gas does not change the colour of dry litmus paper.

Why does an aqueous solution of an acid conduct electricity?

$A$ substance $X$, which is an oxide of a group $2$ element, is used intensively in the cement industry. This element is present in bones also. On treatment with water, it forms a solution which turns red litmus blue. Identify $X$ and write the chemical reactions involved.

To protect against tooth decay,we are advised to brush our teeth regularly. The nature of the toothpaste commonly used is: