
Which of the following are true regarding ideal gas assumptions?
I. Gas molecules have no volume.
II. Pressure is caused by collisions against the walls of the container.
III. All collisions between molecules are elastic.

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Correct Answer: C. I and III only.
According to ideal gas assumptions, all gas molecules are very far away from other gas molecules and their volumes are negligible. Should two gas molecules collide, their collision will be elastic, meaning no kinetic energy is lost (the average kinetic energy can only be changed by heating/cooling the gas). While it is true pressure is caused by the collision of gas molecules against the walls of the container, this is not an assumption for an ideal gas, but rather a general fact of nature. We typically want our ideal gases at low pressures too.
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