1. As the number of molecule-wall collisions increases, the force per collision increases.
2. With more molecules per unit volume, the molecules hit the walls of the container more often.
3. With more molecules in the container, the molecules have higher average speeds.
4. With higher average speeds, on average the molecules hit the walls of the container with more force.
5. None of the Above

3. In the situation above (add He at const T and V), the pressure will increase because:

2. With more molecules per unit volume, the molecules hit the walls of the container more often.