Chapter 11, Problem 11.61P

Interpretation Introduction

Interpretation:

The reason for dilute sodium methoxide and sodium ethoxide being levelled to the same base strength in aqueous solution despite having different pKa values has to be explained.

Concept Introduction:

Levelling effect is observed in case of solvation of acids or base in a solvent.  Thus levelling effect is a phenomenon exhibited by solvents when an acid or base is dissolved in it.

Water forms $H_3{O}^{+}$ ion which is known as hydronium ion and it is formed when lone pair electron on the Oxygen atom is lost to bond with the proton.  Hydronium ion is also behaves as acid as it is capable of losing the proton during the course of reaction.

Any acid that is said to behave stronger acid than hydronium ion, when dissolved in water, forms hydronium ion with water that the strength of the acid is ‘levelled’ to that of the water.

Similarly $O{H}^{-}$ ion is the strongest base in water.  Any other base stronger than $O{H}^{-}$ ion when it dissolved in water its strength is levelled to that of $O{H}^{-}$ ion.