The compound which is used as an oxidising agent in many chemical industries is:

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.

$A$ metal $M$ forms an oxide with the formula $M_{2}O_{3}$. It dissolves in both dilute sulphuric acid and dilute sodium hydroxide solution. Identify the metal and write the chemical equations for the reactions involved.

When soap is scrubbed on a stain of curry on a white cloth,why does it become reddish-brown,and why does it turn yellow again when the cloth is washed with plenty of water?

In a basic aqueous solution,if the concentration of $[OH^-]$ increases,what happens to the $pOH$?

In a basic aqueous solution,how does the basicity of the solution change as the concentration of $[OH^{-}]$ ions decreases?