How can you distinguish between achiral and chiral molecules?

Achiral molecules can be distinguished from chiral ones primarily by their symmetry properties. Achiral molecules possess a plane of symmetry, meaning that there exists a hypothetical plane that can split the molecule into two mirror-image halves. This property indicates that the molecule does not have chirality because it can be superimposed onto its mirror image.

In contrast, chiral molecules lack this type of symmetry and cannot be superimposed on their mirror images, which results in a distinct "handedness." This distinction is crucial in many areas of chemistry, especially in the behavior of enantiomers, which are pairs of chiral molecules that are non-superimposable mirror images of each other.

The other options present aspects that do not accurately describe the distinctions between chiral and achiral molecules. For example, chiral molecules cannot be superimposed on their mirror images, thus the characterization as superimposable does not apply to them. Also, while achiral molecules can rotate plane-polarized light, this property is indicative of optical activity, which is not exclusively tied to chirality. Additionally, chiral molecules often feature one or more stereocenters, not the absence of them, which is a defining characteristic of chirality.