Assertion : At law pressure, van der Waals equation may be expressed as
`pV=RT-(a)/(V)`
Reason : At low pressure, b can be neglected in comparision to V.

Options

A. Assertion and reason both are correct statements and reason is correct explanation for assertion.
B. Assertion and reason both are correct statements but reason is not correct explanation for assertion.
C. Assertion is correct statement but reason is wrong statement.
D. Assertion is wrong statement but reason is correct statement.

Answer

To solve the question, we need to analyze the assertion and reason provided regarding the van der Waals equation at low pressure.

### Step-by-Step Solution:

1. **Understand the Van der Waals Equation**:
The van der Waals equation for one mole of a gas is given by:
\[ \left( P + \frac{a}{V^2} \right)(V - b) = RT \]
where \( P \) is the pressure, \( V \) is the volume, \( T \) is the temperature, \( R \) is the universal gas constant, \( a \) accounts for the attraction between particles, and \( b \) accounts for the volume occupied by the gas particles.

2. **Consider Low Pressure**:
At low pressure, the volume \( V \) of the gas is large. This means that the term \( b \) (which represents the volume occupied by gas molecules) becomes negligible compared to \( V \). Thus, we can simplify the equation.

3. **Neglect the \( b \) Term**:
Under low pressure conditions, we can approximate the equation as:
\[ P + \frac{a}{V^2} \approx \frac{RT}{V} \]
Therefore, we can rearrange it to:
\[ P \approx \frac{RT}{V} - \frac{a}{V^2} \]

4. **Rearranging the Equation**:
We can multiply both sides by \( V \) to eliminate the fraction:
\[ PV \approx RT - \frac{a}{V} \]
This leads us to the assertion:
\[ PV = RT - \frac{a}{V} \]

5. **Conclusion on Assertion and Reason**:
- **Assertion**: The assertion states that at low pressure, the van der Waals equation can be expressed as \( PV = RT - \frac{a}{V} \). This is correct based on our derivation.
- **Reason**: The reason states that at low pressure, \( b \) can be neglected in comparison to \( V \). This is also correct since \( V \) is large, making \( b \) negligible.

Thus, both the assertion and reason are correct.

### Final Answer:
Both the assertion and reason are correct.