Behave most like an ideal gas — States of Matter Chemistry Question
Question
Behave most like an ideal gas
H2(g) molecules at 10-3 atm and 200°C
O2(g) molecules at 20 atm and 200°C
SO2(g) molecules at 20 atm and 200°C
NH3(g) molecules at 20 atm and 200°C
NH3(g) molecules at 20 atm and 300°C
💡 Solution & Explanation
STEPS:
1. Understand the Conditions for Ideal Behavior: Gases behave most "ideally" when the assumptions of the Kinetic Molecular Theory are best met. This occurs when the actual volume of the gas molecules is negligible compared to the container volume and when there are no significant intermolecular attractions between molecules.
2. Identify Favorable Physical Conditions: Gases approach ideal behavior at low pressures (where molecules are far apart) and high temperatures (where molecules move too fast for attractive forces to take effect).
3. Compare Pressures: Looking at the options, Choice A has a pressure of atm (0.001 atm), while all other options (B, C, D, and E) are at a much higher pressure of 20 atm. Low pressure is the most significant factor in reducing molecular interactions.
4. Evaluate Molecular Identity and Intermolecular Forces (IMFs): Smaller, nonpolar molecules with weaker IMFs behave more ideally than large or polar molecules.
* (Option A): Extremely small and nonpolar with the weakest possible London dispersion forces.
* (Option B): Nonpolar but larger than , with stronger dispersion forces.
* and (Options C, D, E): These are polar molecules with significant dipole-dipole attractions (and hydrogen bonding in the case of ), which cause them to deviate greatly from ideal behavior.
5. Conclusion: Because Option A combines the lowest pressure with the weakest intermolecular forces, it is the environment where molecules are most likely to behave like independent, ideal particles.
WHY_OTHERS_WRONG:
- B, C, D, and E: These options all feature a high pressure of 20 atm. At high pressures, gas molecules are forced closer together, making their own volume significant and allowing intermolecular attractions to interfere with ideal movement.
- C, D, and E ( and ): These molecules are polar. Their strong internal dipoles mean they attract each other much more than or would, causing them to "stick" together slightly and deviate from the ideal gas law.
- E ( at 300°C): While the higher temperature slightly improves ideality compared to at 200°C, the high pressure and polar nature of the ammonia molecule still make it far less ideal than hydrogen gas at a near-vacuum pressure ( atm).