Which of the following is a mismatched set ?

Column (A)     Column (B)       Column (C)

Correct Answer:
Slaked lime      CaO      Used for lowering the acidity of soil

Explanation:

Let us analyze each set provided in the columns to identify the mismatched pair:

1. Plaster of Paris:
Chemical Formula:

CaSO₄·$\frac{1}{2}$H₂O

2. Gypsum:
Chemical Formula: CaSO₄·2H₂O (Calcium sulfate dihydrate)
Use: Gypsum products are widely used in dentistry for making impressions and models.
Status: Correctly matched.

3. Bleaching powder:
Chemical Formula: CaOCl₂ (Calcium hypochlorite)
Use: It is used as a bleaching agent in laundries for bleaching cotton and linen clothes.
Status: Correctly matched.

4. Slaked lime:
Chemical Formula: The chemical name of slaked lime is calcium hydroxide, and its formula is Ca(OH)₂. However, the given formula in the table is CaO, which is actually quicklime (Calcium oxide).
Use: Although calcium compounds are used for lowering soil acidity (liming), the match between the name "Slaked lime" and formula "CaO" is incorrect.
Status: Mismatched set.

Hence, the set containing Slaked lime      CaO      Used for lowering the acidity of soil is the mismatched set.