Question

what is the conjugate acid of hso₄⁻ in the reaction below?
h₂so₄(aq) + h₂o(l) ⇌ h₃o⁺(aq) + hso₄⁻(aq)
a. h₂o
b. so₄²⁻
c. h₃o⁺
d. h₂so₄

Explanation:

To find the conjugate acid of \( \text{HSO}_4^- \), we use the definition of conjugate acid - base pairs: a conjugate acid is formed when a base gains a proton (\( \text{H}^+ \)). The formula for \( \text{HSO}_4^- \) gaining a proton (\( \text{H}^+ \)) is \( \text{HSO}_4^-+\text{H}^+
ightarrow\text{H}_2\text{SO}_4 \). Let's analyze the reaction given: \( \text{H}_2\text{SO}_4(aq)+\text{H}_2\text{O}(l)
ightleftharpoons\text{H}_3\text{O}^+(aq)+\text{HSO}_4^-(aq) \). If we reverse the reaction (looking at the reverse direction for the formation of the conjugate acid of \( \text{HSO}_4^- \)), \( \text{HSO}_4^- \) acts as a base and accepts a proton to form \( \text{H}_2\text{SO}_4 \).

• Option A: \( \text{H}_2\text{O} \) is a reactant in the forward reaction and is a base (accepts \( \text{H}^+ \) to form \( \text{H}_3\text{O}^+ \)), not the conjugate acid of \( \text{HSO}_4^- \).
• Option B: \( \text{SO}_4^{2 - } \) would be the conjugate base of \( \text{HSO}_4^- \) (since \( \text{HSO}_4^- \) donates a proton to form \( \text{SO}_4^{2 - } \)), not the conjugate acid.
• Option C: \( \text{H}_3\text{O}^+ \) is the conjugate acid of \( \text{H}_2\text{O} \), not related to \( \text{HSO}_4^- \)'s conjugate acid.
• Option D: \( \text{H}_2\text{SO}_4 \) is formed when \( \text{HSO}_4^- \) accepts a proton, so it is the conjugate acid of \( \text{HSO}_4^- \).

Answer:

D. \( \text{H}_2\text{SO}_4 \)