Problem: Assuming that the van der Waals equation predictions are accurate, account for why the pressure of CH4 is lower than that predicted for an ideal gas.A) The pressure is lower than the ideal gas because there are stronger intermolecular forces and the atoms are smaller. B) The pressure is lower than the ideal gas because there are weaker intermolecular forces and the atoms are smaller. C) The pressure is lower than the ideal gas because there are stronger intermolecular forces and the atoms are larger. D) The pressure is lower than the ideal gas because there are weaker intermolecular forces and the atoms are larger

FREE Expert Solution

Van der Waals equation takes into account attractive forces in a (polarity coefficient) and size in b (size coefficient): 

$\boxed{\mathbf{P}\mathbf{=}\frac{\mathbf{nRT}}{(\mathbf{V}\mathbf{-}\mathbf{nb})}\mathbf{-}\mathbf{a}\frac{{\mathbf{n}}^{\mathbf{2}}}{{\mathbf{V}}^{\mathbf{2}}}}$

For CH₄: 

• a = 2.25 L² atm/mol² → higher value → lower pressure 
• b = 0.0428 L/mol → higher value than other molecules

While the ideal gas equation does not:

$\mathbf{P}\mathbf{=}\frac{\mathbf{nRT}}{\mathbf{V}}$