Let's analyze the given reaction and each option to determine the correct answer.
The reaction given is:
[tex]\[ \text{CH}_3\text{CO}_2\text{H} \rightleftharpoons \text{H}_3\text{O}^+ + \text{CH}_3\text{CO}_2^- \][/tex]
This is an equilibrium reaction where acetic acid (CH[tex]\(_3\)[/tex]CO[tex]\(_2\)[/tex]H) dissociates in water to form hydronium ions (H[tex]\(_3\)[/tex]O[tex]\(^+\)[/tex]) and acetate ions (CH[tex]\(_3\)[/tex]CO[tex]\(_2^-\)[/tex]).
Understanding Acid and Base Behavior:
1. Acid: A substance that donates a proton (H[tex]\(^+\)[/tex]).
2. Base: A substance that accepts a proton.
In this reaction:
- [tex]\(\text{CH}_3\text{CO}_2\text{H}\)[/tex] (acetic acid) donates a proton to water.
- Water (H[tex]\(_2\)[/tex]O) accepts a proton from acetic acid to form [tex]\(\text{H}_3\text{O}^+\)[/tex] (hydronium ion).
Identifying Conjugate Pairs:
- When an acid loses a proton, it forms its conjugate base.
- When a base gains a proton, it forms its conjugate acid.
In this case:
- [tex]\(\text{CH}_3\text{CO}_2\text{H}\)[/tex]---→---[tex]\(\text{CH}_3\text{CO}_2^-\)[/tex] + [tex]\(\text{H}_3\text{O}^+\)[/tex]
- Acetic acid ([tex]\(\text{CH}_3\text{CO}_2\text{H}\)[/tex]) acts as an acid by donating a proton to water.
- The acetate ion ([tex]\(\text{CH}_3\text{CO}_2^-\)[/tex]) is the conjugate base of acetic acid.
- The hydronium ion ([tex]\(\text{H}_3\text{O}^+\)[/tex]) is the conjugate acid of water.
Evaluating Options:
A) [tex]\(\text{CH}_3\text{CO}_2\text{H}\)[/tex] is a base, and [tex]\(\text{H}_3\text{O}^+\)[/tex] is its conjugate acid.
- False: [tex]\(\text{CH}_3\text{CO}_2\text{H}\)[/tex] is an acid, not a base.
B) [tex]\(\text{H}_3\text{O}^+\)[/tex] is an acid, and [tex]\(\text{CH}_3\text{CO}_2^-\)[/tex] is its conjugate base.
- False: The conjugate base of [tex]\(\text{H}_3\text{O}^+\)[/tex] would be water (H[tex]\(_2\)[/tex]O), not [tex]\(\text{CH}_3\text{CO}_2^-\)[/tex].
C) [tex]\(\text{CH}_3\text{CO}_2\text{H}\)[/tex] is an acid, and [tex]\(\text{CH}_3\text{CO}_2^-\)[/tex] is its conjugate base.
- True: [tex]\(\text{CH}_3\text{CO}_2\text{H}\)[/tex] donates a proton, making it an acid, and [tex]\(\text{CH}_3\text{CO}_2^-\)[/tex] is the resulting conjugate base.
D) [tex]\(\text{H}_3\text{O}^+\)[/tex] is an acid, and [tex]\(\text{CH}_3\text{CO}_2\text{H}\)[/tex] is its conjugate base.
- False: The conjugate base of [tex]\(\text{H}_3\text{O}^+\)[/tex] is water, not [tex]\(\text{CH}_3\text{CO}_2\text{H}\)[/tex].
Therefore, the correct answer is:
C) [tex]\(\text{CH}_3\text{CO}_2\text{H}\)[/tex] is an acid, and [tex]\(\text{CH}_3\text{CO}_2^-\)[/tex] is its conjugate base.
