What characteristic of ammonia affects its miscibility with oil?

The correct characteristic of ammonia that affects its miscibility with oil is that it is heavier than oil. In general, the miscibility of substances is influenced by their respective densities and polarities. Oil is primarily composed of long hydrocarbon chains, making it a non-polar substance, while ammonia is polar due to the presence of a nitrogen atom bonded to hydrogen atoms.

Being heavier than oil implies that ammonia has a greater density, which does not contribute to solubility in oil. Miscibility refers to the ability of two substances to mix in all proportions without separation, and because of the significant differences in polarity and density between ammonia and oil, they do not mix effectively. The polar nature of ammonia does not interact favorably with the non-polar molecules of oil, leading to poor miscibility. Thus, the density factor plays a crucial role here; the heavier characteristics of ammonia ultimately lead to its tendency to remain separate from oil rather than mixing with it.