Question

The correct order of increasing pH values of the aqueous solutions of baking soda, rock salt, washing soda and slaked lime is:
A.baking soda $ < $ rock salt $ < $ washing soda $ < $ slaked lime
B.rock salt $ < $ baking soda $ < $ washing soda $ < $ slaked lime
C.slaked lime $ < $ washing soda $ < $ rock salt $ < $ baking soda
D.washing soda $ < $ baking soda $ < $ rock salt $ < $ slaked lime

Answer 1

Hint: We should know the molecular formula for the common names of different salts given. To compare the pH we need to check from which acid and base they are made up of.

Complete step by step answer:
Let us check from which acid and base the given salts are made up of:
Baking salt is the common name for sodium bicarbonate, whose molecular formula is . It is the combination of a strong base that is sodium hydroxide, and a weak acid, that is carbonic acid by partial dissociation of acid. The solution will lie in the basic range because of the presence of a strong base with a pH greater than 7.
Rock salt is the common name for sodium chloride whose molecular formula is . It is the combination of a strong base that is sodium hydroxide, and a strong acid, that is hydrochloric acid. A strong acid and base will form a neutral solution with a pH value of 7.
Washing soda is the common name for sodium carbonate, whose molecular formula is . It is the combination of a strong base that is sodium hydroxide, and a strong acid, that is carbonic acid. The solution will lie in the basic range because of the presence of a strong base with a pH greater than 7.
Slaked lime is the common name for calcium hydroxide, whose molecular formula is . It itself is a base and hence its pH will be maximum.

Hence the correct order is B.

Note:
A salt is formed by the neutralization reaction of an acid or a base with the release of solvent molecules such as water. The more basic the solution is higher will be the pH.