An aqueous solution turns the red litmus solution blue. Excess addition of which of the following solutions would reverse the change?
(A) Baking powder
(C) Ammonium hydroxide solution
(D) Hydrochloric acid
An aqueous solution of base turns red litmus blue .
Therefore, the addition of an acid will lead to the reversal of this change because it will neutralise the base .
Among the given options, the only acid is hydrochloric acid .
So, the correct option is (d) Hydrochloric acid.