What is the $pOH$ value of a $10^{-4} \; M$ aqueous solution of $HCl$?

If a few drops of a concentrated acid accidentally spill over the hand of a student,what should be done?

Which gas is released when acid reacts with metal?

Dry $HCl$ gas does not change the colour of dry blue litmus. Give reason.

$(i)$ Give an example of a strong base and a weak base.

$(a)$ Identify the acid and the base whose combination forms the common salt that you use in your food. Write its formula and chemical name of this salt. Name the source from where it is obtained.
$(b)$ What is rock salt? Mention its colour and the reason due to which it has this colour.
$(c)$ What happens when electricity is passed through brine? Write the chemical equation for it.