To Do Any Acid-Base Problem

1. Know the definition of an acid and a base in both the Lowry-Bronsted sense and the Lewis sense.

2. Any acid-base equilibrium reaction favors the weaker acid. (i.e. know how to predict which way an acid-base reaction lies from the pKa)

3. Know what factors effect the strength of an acid. This is most easily accomplished by determining which conjugate base is most stable.

Important factors in determining conjugate base stability:

Conjugate bases of Lowry-Bronsted acids are normally anions.

Anions which can handle a negative charge better are more stable

factors to consider: a. Size of the atom which has the charge

b. electronegativity of atom which has the charge

c. dispersing the charge by induction

d. hybridization of atom with the charge

e. spreading out the charge by resonance

Practice Problems:

Given the following equilibrium reactions which side of the equation do they favor?

HI + Cl- ----> HCl + I-

Predict the stronger acid out of the following pairs:

CH₃CHFCH₂COOH or CH₃CH₂CHFCOOH

CF₃CH₂OH or CBr₃CH₂OH

Predict the stronger base out of the following pairs:

OH- or F-

OH- or HS-

CH₃CH₂O- or CH₃COO-

For the above bases draw the conjugate acids and predict which is the stronger acid.