Using the data in the table, which of the conjugate bases listed below is the strongest base?
Acid Ka
HOAc 1.8×10-5
HCHO2 1.8×10-4
HClO 3.0×10-8
HF 6.8×10-4
A) OAc-
B) ClO-
C) CHO2-
D) F-
E) OAc-+ and CHO2-
Please select the best answer from the above multiple choice and explain thanks.
The Correct Answer and Explanation is:
The correct answer is: B) ClO⁻
Explanation:
To determine the strongest conjugate base, we need to understand the inverse relationship between the strength of an acid and the strength of its conjugate base:
- A weaker acid (lower Ka) has a stronger conjugate base.
- A stronger acid (higher Ka) has a weaker conjugate base.
Let’s list the acids with their Ka values in ascending order (from weakest acid to strongest):
| Acid | Ka | Conjugate Base |
|---|---|---|
| HClO | 3.0 × 10⁻⁸ | ClO⁻ |
| HOAc (acetic acid) | 1.8 × 10⁻⁵ | OAc⁻ |
| HCHO₂ (formic acid) | 1.8 × 10⁻⁴ | CHO₂⁻ |
| HF | 6.8 × 10⁻⁴ | F⁻ |
From this, we can see that HClO is the weakest acid because it has the smallest Ka. Therefore, its conjugate base, ClO⁻, must be the strongest base among the choices.
Now let’s consider each choice:
- A) OAc⁻: Comes from HOAc, a stronger acid than HClO. Not the strongest base.
- B) ClO⁻: Comes from HClO, the weakest acid. Strongest base.
- C) CHO₂⁻: Comes from HCHO₂, stronger acid than HOAc and HClO.
- D) F⁻: Comes from HF, the strongest acid here, so its conjugate base is the weakest.
- E) OAc⁻ and CHO₂⁻: Both are weaker bases than ClO⁻, so this is incorrect.
Conclusion:
Because ClO⁻ is the conjugate base of the weakest acid (HClO), it is the strongest base listed. Thus, option B is correct.
