Chapter 2, Problem 2.70P

Interpretation Introduction

Interpretation:

To explain the difference in the observed pK values for P and Q.

Concept introduction:

Acid base reaction or Proton transfer reaction. It is the equilibrium reaction. An acid donates a proton to a based and thus forming conjugate acid and base. The reaction is always involves two acid and bases. It is equilibrium reaction so the position of the equilibrium depends on the strength of the acid and bases. The stronger is the acid that donates proton and the stronger base accept the proton. Then these two forms the conjugate acid and base as shown below in the Fig.

From the Bronsted-Lowry, an acid is a proton donor and from the Lewis electron pairs acceptor. Thus an acid strength is defined as the tendency to donate proton. The decision of an acid is stronger is based on the compound donating proton. If the compound readily donates the proton then it is strong acid. The strong acid is determined using the acidity constant, Ka. So larger the Ka value stronger the acid. Moreover for exponent value it is conveniently measured by pKa values.

pKa = -log Ka

So, smaller the pKa, stronger is the acid.