Why does the pressure inside a container of gas increase when more gas is added to the container, assuming volume and temperature remain constant?

• A. Because adding more gas decreases the volume, causing the molecules to be closer together.
• B. Because adding more gas lowers the temperature, which increases the pressure.
• C. Because adding more gas causes the molecules to move slower, increasing the pressure.
• D. Because adding more gas increases the number of molecules, leading to more frequent collisions with the container walls.

Answer: (D)

Verified step by step guidance

1. Recall the ideal gas law, which relates pressure (P), volume (V), number of moles (n), gas constant (R), and temperature (T): \(P \times V = n \times R \times T\).
2. Since the volume (V) and temperature (T) are constant in this problem, any change in pressure (P) must be due to a change in the number of gas molecules (n).
3. Adding more gas increases the number of molecules inside the container, which means there are more particles moving and colliding with the container walls.
4. Pressure is caused by collisions of gas molecules with the container walls; more molecules lead to more frequent collisions per unit time, thus increasing the pressure.
5. Therefore, the pressure increases because the increased number of gas molecules results in more collisions, not because of changes in volume, temperature, or molecular speed.