Which one of the following gases would deviate the least from ideal gas behavior under standard conditions?

• A. He
• B. CO_2
• C. SO_2
• D. NH_3

Answer: (A)

Verified step by step guidance

1. Recall that ideal gas behavior assumes no intermolecular forces and that gas particles occupy no volume. Real gases deviate from ideal behavior due to intermolecular attractions and finite molecular size.
2. Understand that gases with smaller, nonpolar molecules and weaker intermolecular forces tend to behave more ideally. Conversely, gases with larger, polar molecules or hydrogen bonding deviate more.
3. Examine the given gases: He (helium) is a noble gas with very small, monoatomic, nonpolar particles and negligible intermolecular forces; CO_2 and SO_2 are larger molecules with polar characteristics; NH_3 is polar and capable of hydrogen bonding.
4. Recognize that under standard conditions (usually 1 atm and 25°C), helium's weak intermolecular forces and small size cause it to deviate the least from ideal gas behavior.
5. Conclude that among the options, helium (He) will behave closest to an ideal gas because it has the smallest molecular size and weakest intermolecular forces.