Hydrogen () and Helium () gases experimentally show a positive deviation () from ideal behavior even at standard room temperatures. What is the fundamental theoretical reason for this anomaly?

Question

Hydrogen ($H_2$) and Helium ($He$) gases experimentally show a positive deviation ($Z > 1$) from ideal behavior even at standard room temperatures. What is the fundamental theoretical reason for this anomaly?

Prashant Kotian · Accepted Answer

Correct answer: B. For and , the intermolecular forces of attraction are virtually non-existent, meaning their van der Waals constant '' is extremely small. Therefore, the term is negligible at normal temperatures. The equation becomes , leading to . Thus, repulsive forces (size effect '') dominate, and at all pressures.

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