Which of the following molecules would exhibit the most ideal behavior under standard conditions?

• A. H_2O
• B. NH_3
• C. He
• D. CO_2

Answer: (C)

Verified step by step guidance

1. Recall that ideal gas behavior is best approximated by gases composed of small, nonpolar, monatomic molecules with minimal intermolecular forces.
2. Analyze each molecule: H_2O and NH_3 are polar molecules with hydrogen bonding, which causes deviations from ideal behavior.
3. CO_2 is a linear molecule with some polarity but also experiences intermolecular forces like van der Waals interactions, leading to non-ideal behavior.
4. He (helium) is a noble gas, monatomic, nonpolar, and has very weak intermolecular forces, making it the closest to an ideal gas under standard conditions.
5. Therefore, the molecule that exhibits the most ideal behavior is the one with the least intermolecular forces and simplest structure, which is He.