Question

What is an alkali ? what is indicator?​

Answer 1

Answer:

An acid-alkali indicator or pH indicator is a coloring agent, usually a weak acid or base, which changes its color in response to the pH value of an aqueous solution (i.e. in response to a change in the hydrogen ion concentration).

Answer 2

Answer:

1. water soluble bases are called alkalis.
2. An indicator is a dye which changes it's colour when come in contact with an acid or a base