The $pH$ scale is applicable to which of the following?

How is an aqueous solution with $pH = 2$ compared to an aqueous solution with $pH = 4$?

$(a)$ 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.

Why does $1 \, M \, HCl$ solution have a higher concentration of $H^{+}$ ions than $1 \, M \, CH_{3}COOH$ solution?

What is the molecular mass of $NaOH$?

Which of the following gives the correct increasing order of acidic strength?