Rationale
Gas CO2 particles occupy more space.
When dry ice sublimates, solid CO2 transitions directly to gas, increasing the number of gas molecules in the container. This increase in the number of gas particles leads to a higher frequency of collisions with the container walls, thereby raising the pressure.
A) CO2 particles actually exert more force on the container walls when they are in the gas phase compared to when they are solid, not less. In the gas state, molecules are free to move and collide with the walls, leading to increased pressure. Therefore, this statement misrepresents the behavior of gas molecules.
B) The speed of gas CO2 molecules does not increase simply because CO2 is a solid. Instead, gas molecules move faster than solid molecules due to increased kinetic energy. The transition from solid to gas involves an increase in kinetic energy, but this choice does not address the reason for pressure increase related to spatial occupancy.
D) CO2 molecules do not combine to form larger molecules in the gas phase; they remain as individual CO2 molecules. The increase in pressure is due to the greater number of gas molecules that arise from sublimation, not from the formation of larger molecules. This choice is incorrect as it fundamentally misunderstands the nature of gas behavior.
Conclusion
The increase in pressure exerted by carbon dioxide on the walls of a sealed container during sublimation results from the gas CO2 particles occupying more space. As dry ice sublimates, the number of gas molecules increases, leading to more collisions with the walls and consequently higher pressure. The incorrect options misinterpret gas behavior or focus on unrelated phenomena, emphasizing the crucial role of spatial occupancy in gas pressure dynamics.