Which of the following salts is formed by the neutralization of a weak acid and a strong base?

What is the molecular mass of $NaOH$?

Write balanced chemical equations for the following:
$(i)$ Bleaching powder is kept open in air.
$(ii)$ Blue crystals of copper sulphate are heated.
$(iii)$ Chlorine gas is passed through dry slaked lime.

Which one of the following can be used as an acid-base indicator by a visually impaired student?

In one of the industrial processes used for the manufacture of sodium hydroxide,a gas $X$ is formed as a by-product. The gas $X$ reacts with lime water to give a compound $Y$,which is used as a bleaching agent in the chemical industry. Identify $X$ and $Y$ and provide the chemical equations for the reactions involved.

The marble statues are often slowly corroded when kept in the open for a long time. Give a suitable reason.