Question

Why ethanol is completely miscible in water while the corresponding alkane can not?

Answer 1

Ethanol has a polar –OH group, which hydrogen bonds to water; which makes ethanol soluble. Ethane, which is composed, of carbon and hydrogen only, has no polar group and is not water-soluble. If a Hydrogen is bonded to a strongly electronegative atom (Nitrogen, Fluorine or Oxygen) it can form hydrogen bonds, since both water and alcohols have an OH they can hydrogen bond with each other, this makes them miscible. Miscible meaning mixing completely to form a homogeneous solution.

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