Final answer:
O2 does not float in air even though its molecular weight is slightly higher than the average molecular weight of air, as air already contains about 20% oxygen and other factors such as temperature and pressure also affect the buoyancy of gases.
Step-by-step explanation:
If the molecular weight of air is 28.96 g/mol and O2 is 32 g/mol, does O2 float in air? The answer is no, O2 does not float in air despite its molecular weight being slightly higher than the average molecular weight of air. This is because the composition of air is largely nitrogen (N2), which has a molecular weight of approximately 28 g/mol, and oxygen (O2), which has a molecular weight of 32 g/mol. Since air already contains approximately 20% oxygen, the difference in molecular weights does not create a significant buoyant force for oxygen to 'float' in air.
The concept of gases floating is related to their densities in comparison to the density of the surrounding medium (in this case, air). The average molecular weight of air is slightly lower than that of O2, but the density of a gas also depends on temperature and pressure as dictated by the ideal gas law. Conditions such as higher temperature can decrease the density of a gas, potentially causing it to rise in the surrounding air as seen with hot air balloons. However, at standard conditions, oxygen molecules are evenly dispersed throughout the air and do not separately float or sink due to their molecular weight.