Match (A) mole, (B) Avogadro's number, (C) 22.4 L, (D) vapour density, (E) empirical formula with its description given below.
It is equal to half of the molecular mass

Answer

To solve the problem of matching the terms with their descriptions, we will go through each term and its definition. The description we need to match is: "It is equal to half of the molecular mass."

### Step-by-Step Solution:

1. **Identify the Terms**: We have five terms to match:
- (A) mole
- (B) Avogadro's number
- (C) 22.4 L
- (D) vapour density
- (E) empirical formula

2. **Define Each Term**:
- **Mole (A)**: The mole is a unit that measures the amount of substance. It contains \(6.022 \times 10^{23}\) particles (atoms, molecules, ions, etc.).
- **Avogadro's Number (B)**: This is the numerical value \(6.022 \times 10^{23}\), representing the number of particles in one mole of a substance.
- **22.4 L (C)**: This is the volume occupied by one mole of an ideal gas at standard temperature and pressure (STP).
- **Vapour Density (D)**: Vapour density is defined as the molecular mass of a gas divided by 2. This means it is equal to half of the molecular mass of the gas.
- **Empirical Formula (E)**: The empirical formula represents the simplest whole-number ratio of atoms in a compound.

3. **Match the Description**:
- The description states: "It is equal to half of the molecular mass."
- From our definitions, we see that vapour density (D) is defined as the molecular mass divided by 2, which matches the description perfectly.

4. **Conclusion**:
- Therefore, the correct match for the description "It is equal to half of the molecular mass" is **(D) vapour density**.

### Final Answer:
- The correct match is **(D) vapour density**.