Assertion (A): Dimethyl ether is less volatile than ethyl alcohol.
Reason (R): Dimethyl ether has greater vapour pressure than ethyl alcohol

Options

A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true but R is NOT the correct explanation of A
C. A is true but R is false
D. A is false and R is True

Explanation

To solve the assertion and reason question, we will analyze both the assertion (A) and the reason (R) step by step.

### Step 1: Understand the Assertion (A)
The assertion states that "Dimethyl ether is less volatile than ethyl alcohol."

**Explanation**:
- Volatility refers to the tendency of a substance to vaporize. A more volatile substance has a higher vapor pressure at a given temperature.
- Dimethyl ether (CH3OCH3) and ethyl alcohol (CH3CH2OH) have the same molecular formula (C2H6O) but different structures and properties.

### Step 2: Understand the Reason (R)
The reason states that "Dimethyl ether has greater vapor pressure than ethyl alcohol."

**Explanation**:
- Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid at a given temperature.
- Dimethyl ether does indeed have a higher vapor pressure compared to ethyl alcohol due to the absence of strong intermolecular forces like hydrogen bonding, which are present in ethyl alcohol.

### Step 3: Analyze Intermolecular Forces
- Ethyl alcohol exhibits hydrogen bonding due to the presence of the -OH (hydroxyl) group, which leads to stronger intermolecular attractions.
- Dimethyl ether, on the other hand, does not have hydrogen bonding and thus has weaker intermolecular forces.

### Step 4: Compare Volatility
- Since ethyl alcohol has stronger intermolecular forces (due to hydrogen bonding), it is less volatile than dimethyl ether, which has weaker forces and thus higher volatility.

### Conclusion
- The assertion (A) is **false** because dimethyl ether is actually **more volatile** than ethyl alcohol.
- The reason (R) is **true** because dimethyl ether does have a greater vapor pressure than ethyl alcohol.

### Final Answer
- Assertion (A) is false, and Reason (R) is true.