Van der Waals Constant a Formula:
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Definition: Van der Waals constant 'a' represents the magnitude of attractive forces between gas molecules. It corrects the ideal gas law for intermolecular forces.
Purpose: This calculator determines the 'a' constant based on the critical temperature and 'b' constant of a gas.
The calculator uses the formula:
Where:
Explanation: The formula relates the constants at the critical point where the distinction between gas and liquid phases disappears.
Details: These constants are crucial for accurate gas behavior predictions, especially at high pressures and low temperatures where real gases deviate from ideal behavior.
Tips: Enter the Van der Waals constant b (m³/mol) and critical temperature (K). Both values must be > 0.
Q1: What are typical values for Van der Waals constant b?
A: For common gases, b ranges from about 3 × 10⁻⁵ m³/mol (He) to 5 × 10⁻⁵ m³/mol (larger molecules like CO₂).
Q2: What is critical temperature?
A: The highest temperature at which a gas can be liquefied by pressure alone. Above this temperature, no amount of pressure can liquefy the gas.
Q3: Why is the universal gas constant used?
A: R appears in the derivation of the Van der Waals equation from the critical point conditions.
Q4: What units does this calculator use?
A: SI units are used throughout (m³, mol, K, Pa) for consistency with standard physical chemistry practice.
Q5: How accurate is this calculation?
A: This provides theoretical values based on critical point conditions. Experimental values may differ slightly.