What is Not a Set of Conjugates?

[TT0]

Homework Statement

Which pairing is not a set of conjugates?

A. OH^1– and H₂O
B. HC₂H₃O₂ and C₂H₃O₂^1–
C. HCl and Cl^1–
D. NH₃ and NH₄¹⁺
E. H₂SO₄ and SO₄^2–

Homework Equations

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The Attempt at a Solution

I couldn't choose because conjugates, from what I learnt, is basically an acid or a base and its equivalent with more or less protons. All of the pairs have protons as their only difference. The only special case is E with 2 proton difference, but I know H₂SO₄ is sulfuric acid and when it has donated its protons it will become SO₄^2–. So it seems to me E would also be conjugate. However, the answer is E. Could someone explain to me why E is not a pair of conjugates?

 

[Borek]

conjugates, from what I learnt, is basically an acid or a base and its equivalent with more or less protons

That's imprecise. Acid and its conjugate base differ by exactly one proton.

Please remember, that sulfuric acid dissociates stepwise:

H₂SO₄ ↔ HSO₄^- + H⁺

and

HSO₄^- ↔ SO₄^2- + H⁺

Can you show now conjugate pairs in this process?

 

[TT0]

I see thanks Borek