Question

Under non-ideal conditions, why was the pressure lower using the van der Waals equation?

• A. The attractive forces between the molecules repels them from each other
• B. The attraction between the molecules increases
• C. The attractive forces between the molecules makes them larger
• D. The attractive forces between the molecules makes them smaller
• E. The pressure was greater

Answer 1

The correct option is B The attraction between the molecules increases

Under non-ideal conditions, the pressure was lower using the van der Waals equation because of the attraction between the molecules increases.
$(P+\frac{a{n}^2}{V^2})(V-nb)=nRT$
The value of $a$ increases. The value of $\frac{a{n}^2}{V^2}$ increases and the value of $P$ decreases accordingly.