Consider the sample of gas depicted here. What would the drawing look like if the volume and temperature remained constant while you removed enough of the gas to decrease the pressure by a factor of 2? (a) It would contain the same number of molecules. (b) It would contain half as many molecules. (c) It would contain twice as many molecules. (d) There is insufficient data to say.

Key Concepts

Ideal Gas Law

The Ideal Gas Law relates the pressure, volume, temperature, and number of moles of a gas through the equation PV = nRT. This law helps us understand how changing one variable affects the others, assuming ideal behavior. In this scenario, if the volume and temperature are constant, a decrease in pressure must correspond to a decrease in the number of gas molecules.

Avogadro's Principle

Avogadro's Principle states that equal volumes of gases, at the same temperature and pressure, contain an equal number of molecules. This principle is crucial for understanding how the number of gas molecules changes with pressure when volume and temperature are held constant. Thus, if the pressure is halved, the number of molecules must also decrease to maintain the relationship defined by this principle.

Pressure-Volume Relationship

The pressure-volume relationship, often described by Boyle's Law, indicates that for a given amount of gas at constant temperature, the pressure of the gas is inversely proportional to its volume. In this case, since the volume is constant and the pressure is reduced by half, it implies that the number of gas molecules must also decrease, reinforcing the connection between pressure and the quantity of gas present.