In vander waal's equation of the gas law the constant of a is a measure of

Options

A. intermolecular repulsion
B. intermolecular attraction
C. volume occupied by the molecules
D. relativevelocity of gas molecules

Answer

To solve the question regarding the Van der Waals equation of the gas law and the constant 'A', we can follow these steps:

### Step 1: Understand the Van der Waals Equation
The Van der Waals equation is an adjustment of the ideal gas law that accounts for the behavior of real gases. It is expressed as:
\[ \left( P + \frac{a n^2}{V^2} \right) (V - nb) = nRT \]
where:
- \( P \) = pressure of the gas
- \( V \) = volume of the gas
- \( n \) = number of moles of the gas
- \( R \) = universal gas constant (8.314 J/(mol·K))
- \( T \) = temperature in Kelvin
- \( a \) = constant related to the attraction between gas molecules
- \( b \) = constant related to the volume occupied by gas molecules

### Step 2: Identify the Role of Constant 'A'
In the equation, the constant 'a' is associated with the term \( \frac{a n^2}{V^2} \). This term corrects the pressure of the gas to account for the attractive forces between the gas molecules.

### Step 3: Determine What 'A' Measures
The constant 'a' specifically measures the strength of the intermolecular forces of attraction. The larger the value of 'a', the stronger the attractive forces between the molecules of the gas. This is crucial in differentiating real gases from ideal gases, as ideal gases do not exhibit intermolecular forces.

### Step 4: Conclusion
Based on the understanding of the Van der Waals equation and the role of constant 'a', we can conclude that:
- The constant 'A' is a measure of **intermolecular attraction**.

### Final Answer
The correct option is: **intermolecular attraction**.

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