Question

State whether the following sentence is true or false.
Non-polar compounds are soluble in polar solvent.
(A) True
(B) False

Answer 1

Hint: As there is a common saying that ‘like begets like’, there is also a similar common saying in chemistry that ‘like soluble like’ or ‘like dissolves like’.

Complete answer:The sentence above is false for practical purposes. Technically speaking, the solubility of non-polar solutes in polar solvents is extremely less, which makes us think that they are insoluble.
Now let’s discuss why non-polar solutes are insoluble in polar solvents, by explaining the common saying in chemistry ‘like soluble like’ or ‘like dissolves like’. The saying means that solvents look for some similarity while dissolving the solvent. If a solute is similar to the solvent, that solute will be soluble in the solvent. If it is not, then the solute will be insoluble. The similarity which a solvent looks for is the polarity of solute molecules. In simple words, this can be understood as ‘polar solutes dissolve in polar solvent, and non-polar solute dissolves in non-polar solvent.’
What do you mean by polarity then? What does it mean when you say that something is polar or non-polar? Let’s understand that too as well. Whenever there is a separation of electric charge within a molecule due to the difference in the electronegativity of the two bonded atoms. In case of water molecules, there is a separation of electric charge within the molecule since oxygen is more electronegative than the covalently bonded hydrogen atoms. Oxygen in the molecule pulls the bonded electron pair towards itself, which results in oxygen acquiring a partial negative charge, and hydrogen acquiring a partial positive charge. Such covalent bonds, where the electron pair shifts towards a more electronegative atom in a polar compound, is known as a ‘polar bond’. When there is no such separation of electric charge within a molecule, that molecule is known as a non-polar molecule.
So nonpolar compounds are insoluble in polar solvent.

Hence, the correct answer is option(B) i.e. False.

Note:Even though we generally say that non-polar solutes don’t dissolve in polar solvent, it is not completely true. In fact there are no two substances which are perfectly insoluble into one another. Oxygen being a non-polar molecule should be insoluble in water by this rule, but there is some small quantity of oxygen that manages to be soluble in the polar solvent named water, which makes the life of aerobic aquatic living organisms possible.