Assertion : When 20 ml of ethanol is mixed with 20ml of water , the volume of resulting solution will be less than 40 ml.
Reason : The hydrogen bond between water and alcohol molecules is weaker than hydrogen bond between the like molecules.

Options

A. If both the assertion and reason are true statement and reason is correct explanation of the assertion .
B. If both the assertion and reason are true statement but reason is not a correct explanation of the assertion .
C. If the assertion is false but the reason is a true statement.
D. If both assertion and reason are false statements.

Explanation

To solve the question, we need to analyze the assertion and the reason provided.

### Step 1: Understand the Assertion
The assertion states that when 20 ml of ethanol is mixed with 20 ml of water, the volume of the resulting solution will be less than 40 ml.

### Step 2: Analyze the Mixing of Ethanol and Water
When ethanol and water are mixed, they form a non-ideal solution. In this case, the volume of the resulting solution is not simply the sum of the volumes of the two liquids (20 ml + 20 ml = 40 ml). Instead, due to the interactions between the molecules of ethanol and water, the total volume can be less than 40 ml.

### Step 3: Understand the Reason
The reason given states that the hydrogen bond between water and alcohol molecules is weaker than the hydrogen bond between like molecules (water-water and ethanol-ethanol). This is a true statement. The weaker interactions between different types of molecules (water and ethanol) compared to the stronger interactions between similar molecules (water-water and ethanol-ethanol) lead to a positive deviation from Raoult's law.

### Step 4: Conclusion on the Assertion and Reason
- The assertion is **false** because when ethanol and water are mixed, the volume is not less than 40 ml; it is typically more than 40 ml due to the positive deviation from Raoult's law.
- The reason is **true** because the hydrogen bonds between unlike molecules (water and ethanol) are indeed weaker than those between like molecules.

### Final Answer
Thus, the correct conclusion is that the assertion is false, but the reason is true.