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Given the equilibrium reaction:

[tex]\[ \text{CH}_3\text{CO}_2\text{H}_{(aq)} \rightleftharpoons \text{H}_3\text{O}^+_{(aq)} + \text{CH}_3\text{CO}_2^-_{(aq)} \][/tex]

Which of the following statements is correct?

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.

B. [tex]\(\text{H}_3\text{O}^+\)[/tex] is an acid, and [tex]\(\text{CH}_3\text{CO}_2^-\)[/tex] is its conjugate base.

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.

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.


Sagot :

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.