Consider the acid ionization constants given below:

Acid Ka
HOCl 3.5
×
10–8
HCO2H 1.8
×
10–4
HBrO3 ~ 2
HOI 2.0
×
10–11
HClO2 1.1
×
10–2

When the conjugate bases are listed from the strongest to the weakest base, the order is:

Question

Consider the acid ionization constants given below:

Acid	Ka
HOCl	3.5 
×
 10–8
HCO2H	1.8 
×
 10–4
HBrO3	~ 2
HOI	2.0 
×
 10–11
HClO2	1.1 
×
 10–2

When the conjugate bases are listed from the strongest to the weakest base, the order is:

BlackTom AI · Accepted Answer

The problem asks us to order the conjugate bases from strongest to weakest base.
First, recall the relationship between acid strength and conjugate base strength: stronger acids have weaker conjugate bases, and weaker acids have stronger conjugate bases.
Next, list the given acids in order of increasing acidity (i.e., from weakest to strongest acid) based on their Ka values:
- HOI has Ka = 2.0 × 10^−11 (very weak acid), so its conjugate base IO− is relatively strong.
- HOCl has Ka = 3.5 × 10^−8, so its conjugate base OCl− is weaker than IO−.
- HCO2H (formic acid) has Ka = 1.8 × 10^−4, so its conjugate base HCO2− is weaker than OCl− but stronger than ClO2− and BrO3− bases.
- HOClO2 (HClO2) has Ka = 1.1 × 10^−2, so its conjugate base ClO2− is weaker than HCO2− but stronger than BrO3−−base, given the larger Ka.
- HBrO3 has Ka ≈ 2 (a strong acid), so its conjugate base BrO3− is the weakest base among the set.
With this inverse relationship, the strongest base corresponds to the weakest acid, and so the order of conjugate bases from strongest to weakest is:
IO− > OCl− > HCO2− > ClO2− > BrO3−
Now evaluate the provided options:
- Option A: BrO3− > OCl− > ClO2− > HCO2− > OI−
  This reverses the expected strength pattern, placing BrO3− (weakest base) first, which contradicts the acid/base relationship.
- Option B: OI− > OCl− > HCO2− > ClO2− > BrO3−
  This matches the logically derived order: IO− (strongest base) first, then OCl−, then HCO2−, then ClO2−, and BrO3− as the weakest base.
- Option C: OI− > HCO2− > ClO2− > OCl− > BrO3−
  Here OCl− and HCO2− are out of the expected positions relative to each other; the sequence places ClO2− after HCO2− but before OCl−, which misorders them.
- Option D: BrO3− > ClO2− > HCO2− > OCl− > OI−
  This starts with BrO3− as the strongest base, which is incorrect since BrO3− is the conjugate base of a strong acid and should be the weakest base.
- Option E: ClO2− > HCO2− > OCl− > OI− > BrO3−
  This places ClO2− ahead of OCl− and IO−, contradicting the trend that weaker acids yield weaker conjugate bases and thus ClO2− should be weaker than OCl− and IO−.
In summary, Option B faithfully represents the strongest-to-weakest base order based on the given acid strengths, while the other options misorder one or more conjugate bases relative to the acid strength principle.

Consider the acid ionization constants given below: Acid Ka HOCl 3.5 × 10–8 HCO2H 1.8 × 10–4 HBrO3 ~ 2 HOI 2.0 × 10–11 HClO2 1.1 × 10–2 When the conjugate bases are listed from the strongest to the weakest base, the order is:

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