It is possible to obtain oxygen from air by fractional distillation because (a) Oxygen has a lower density than nitrogen. (b) Oxygen has high b.p. than nitrogen. (c) Oxygen is more reactive than nitrogen (d) Oxygen is in a different group of the periodic table from nitrogen.

When faced with a mixture of different substances, scientists and engineers often need a method to separate these substances based on their physical properties. This is where the separation of mixtures comes into play. It's not about changing what's in the mixture but rather about pulling it apart into its individual components.

One of the simplest examples is sorting rocks from sand—using a sieve to take advantage of the size difference. But what if the components are gases? Fractional distillation can be seen as a 'thermal sieve' for this purpose, using not size, but boiling points, to separate substances such as oxygen and nitrogen from the air.

Why is knowing how to separate mixtures important? It's crucial in areas such as pharmaceutical manufacturing for drug purity, in environmental science to remove pollutants, and many more industry applications. It's also fundamental in routine laboratory work, where achieving a pure substance from a mixture is often the first step in the analysis or synthesis of chemical compounds.

Understanding boiling points is key when it comes to separating components by distillation. The boiling point is the temperature at which a substance transitions from liquid to gas. But why do different substances have different boiling points? It's all about the strength of the forces between particles: stronger forces mean higher boiling points.

Here's the thing, the boiling point is a unique and consistent physical property of a pure substance under a given pressure. Water, for example, boils at 100°C at sea level, but this changes with pressure. When fractional distillation is used, like separating oxygen from nitrogen in the air, we utilize their different boiling points. Nitrogen boils at -195.8°C while oxygen has a slightly higher boiling point of -183.0°C. This difference allows for the separation process in a fractionating column, as each gas will condense and can be collected at different levels within the column.

Gases have distinct physical properties that can include density, refractive index, and, crucially for fractional distillation, boiling points. But let's zoom in—what's happening at the molecular level? Gases are made up of particles that are far apart and move rapidly and freely, which explains their ability to fill a container of any size.

These properties not only define how gases behave under different conditions but also how they can be separated from each other. For instance, when we cool gaseous mixtures down to very low temperatures, some components will liquefy before others based on their boiling points. In the separation process, maintaining the right temperature and pressure conditions is essential to ensure that each gas behaves predictably according to its physical properties.

Related to fractional distillation, these unique characteristics among gases allow us to precisely control the process to efficiently and effectively extract pure substances, such as oxygen from air, which is pivotal in various industrial and medical applications.