Assertion: The weight percentage of a compound A in a solution is given by
`% of A=("Mass A")/("Total mass of solution")xx100`
Reason: The mole fraction of a component A is given by, Mole fraction of A
`=("No. of moles of A")/("Total no. of moles of all components")`

Options

A. Statement-I is true, Statement-II is true , Statement-II is correct explanation for Statement-I
B. Statement-I is true, Statement-II is true , Statement-II is `NOT` a correct explanation for statement-I
C. Statement-I is true, Statement-II is false
D. Statement-I is false, Statement-II is true

Answer

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

### Step 1: Analyze the Assertion
The assertion states that the weight percentage of a compound A in a solution is given by:
\[ \% \text{ of A} = \left(\frac{\text{Mass of A}}{\text{Total mass of solution}}\right) \times 100 \]
This formula is indeed correct. The weight percentage (mass percentage) of a component in a solution is calculated by taking the mass of that component and dividing it by the total mass of the solution, then multiplying by 100 to convert it into a percentage.

### Step 2: Analyze the Reason
The reason states that the mole fraction of a component A is given by:
\[ \text{Mole fraction of A} = \frac{\text{No. of moles of A}}{\text{Total no. of moles of all components}} \]
This statement is also correct. The mole fraction is defined as the ratio of the number of moles of a particular component to the total number of moles of all components in the mixture.

### Step 3: Determine the Relationship Between Assertion and Reason
Both statements are correct, but we need to assess whether the reason correctly explains the assertion. The assertion talks about weight percentage, while the reason discusses mole fraction. Although both concepts are related to the composition of solutions, the reason does not provide a direct explanation for the assertion.

### Conclusion
- **Assertion**: Correct
- **Reason**: Correct
- **Explanation**: The reason does not explain the assertion.

Thus, the correct option is that both the assertion and reason are correct, but the reason is not the correct explanation for the assertion.

### Final Answer
**Option B**: Both the assertion and reason are correct, but the reason is not the correct explanation for the assertion.

---