What is a major limitation of simple distillation?

Simple distillation is a technique used to separate components in a mixture based on differing boiling points. Its major limitation is that it is not effective for separating substances that have boiling points that are very close to each other. When the boiling points of the components in a mixture are too similar, the system may not achieve sufficient separation, leading to the condensation of both components rather than isolating them individually. This is because, during the distillation process, both substances can easily vaporize at similar temperatures, making it difficult to obtain a pure sample of one component.

The other options present characteristics that do not accurately describe the limitations of simple distillation. For example, while high temperatures are sometimes used, they are not a necessary condition for the process. It is also true that simple distillation can be applied to gas mixtures as long as they can be liquefied, going beyond just liquids. Further, the notion that it can only be used once is incorrect; the apparatus can be reused for multiple distillations. Thus, option B effectively captures the fundamental limitation of the method regarding the separation efficiency related to closely boiling components.