Which of the following concerning the ideal gas law is/are true?
1. Pressure is directly proportional to volume when temperature and moles of gas are held constant.
2. Pressure is directly proportional to moles of gas when temperature and volume are held constant.
3. Volume is inversely proportional to temperature when the pressure and moles of gas are held constant.
1 only
2 only
3 only
1 and 2 only
2 and 3 only