The values of two phenolic acids at are given below

CHEMISTRY · Multi-part · AP · Chemistry · Acids and Bases · Acids and Bases

Problem

The

pK_a

values of two phenolic acids at

298\,\text{K}

are given below. • Phenol:

pK_a = 10.00

•

p

-Nitrophenol:

pK_a = 7.15

For any acid, the standard free energy of deprotonation is related to its

pK_a

\Delta G^\circ = 2.303\, R\, T\, pK_a,

where

R = 8.314\,\text{J}\cdot\text{mol}^{-1}\cdot\text{K}^{-1}

and

T = 298\,\text{K}

. (1) Part 1: (a) Calculate

\Delta G^\circ

(in

\text{kJ}\cdot\text{mol}^{-1}

) for the deprotonation of phenol. (2) Part 2: (b) Calculate

\Delta G^\circ

(in

\text{kJ}\cdot\text{mol}^{-1}

) for the deprotonation of

p

-nitrophenol. (3) Part 3: (c) Determine

\Delta\Delta G^\circ

, the difference in standard free energy of deprotonation between the two acids, and state which conjugate base is thermodynamically more stable.