Question

Arrange the conjugate bases of these weak acids in order of increasing base strength (1 = weakest and 5 = strongest).

Options:
a) C₆​H₅​O⁻
b) CH₂​ClCO₂⁻
c) HCO₂⁻​
d) CH₃​CO₂⁻​
e) C₆​H₅​CO₂​⁻

Answer 1

The conjugate bases of weak acids are arranged in order of increasing strength, from the weakest C₆H₅CO₂⁻ (1) to the strongest CH₃CO₂⁻ (5). This is based on the inverse relationship between the strength of the parent acid and the strength of its conjugate base.

Step-by-step explanation:

The conjugate bases of the given weak acids arranged in order of increasing base strength (where 1 is the weakest and 5 is the strongest) are:

1. C₆H₅CO₂⁻
2. CH₂ClCO₂⁻
3. C₆₅O⁻
4. HCO₂⁻
5. CH₃CO₂⁻

The base strength of a conjugate base is inversely related to the strength of its conjugate acid. The weaker the acid, the stronger the conjugate base. Therefore, you can judge the relative strength of the bases by considering the known acidity of the related acids. Benzene carboxylate (C₆H₅CO₂⁻) comes from benzoic acid which is a relatively weak acid, hence its conjugate base is the weakest among those listed.

Acetate ion (CH₃CO₂⁻) comes from acetic acid, which is stronger than benzoic acid but still a weak acid, making acetate the strongest conjugate base here.