When red litmus paper is added to limewater, then what will be the change in litmus paper? Give reason. Write the chemical formula of limewater also.

The litmus paper will turn blue; Ca (OH) ₂

Explanation:

Limewater is a dilute aqueous solution of calcium hydroxide.

Ca (OH) ₂ (aq) ⟶ Ca²⁺ (aq) + 2OH⁻ (aq)

Limewater contains hydroxide ions. They cause the limewater to be basic.

Litmus is a mixture of dyes extracted from lichens. They are weak acids with complicated formulas.

Let's just write the formula for litmus as HLit.

The hydroxide ions from limewater react with the H of litmus to form a salt - the base form - and water.

HLit + OH⁻ ⟶ Lit⁻ + H₂O

acid form base form

red blue

The base form of litmus is blue, so

Red litmus turns blue in the presence of limewater.