A student mixed equal volumes of hydrochloric acid and sodium hydroxide solution of same concentrations in a beaker and tested the pH of the resulting mixture with a pH paper. What will be the colour of pH paper in this case?
(1)
(2) yellow
(3) green
(4) blue

Correct answer: (3) green

Explanation: Hydrochloric acid is a strong acid and sodium hydroxide is a strong base, so they will neutralize each other as the conc. of H⁺ and OH^- ion will become equal. The colour of the pH paper for neutral solutions is green.