To solve the problem of identifying the acid-conjugate base pairs in the given reaction, we need to understand the concept of conjugate acid-base pairs in the context of the Brønsted-Lowry acid-base theory.
The Brønsted-Lowry theory defines an acid as a proton (H⁺) donor and a base as a proton (H⁺) acceptor. When an acid donates a proton, it becomes its conjugate base, and when a base accepts a proton, it becomes its conjugate acid.
Let's analyze the given reaction to identify the acid-conjugate base pairs:
[tex]\[
HF + H_2O \rightarrow H_3O^+ + F^-
\][/tex]
1. Identify the acid and base on the reactant side:
- HF is the acid because it donates a proton (H⁺) to water (H₂O).
- H₂O is the base because it accepts the proton from HF.
2. Identify the conjugate acid and conjugate base on the product side:
- When HF donates a proton, it becomes F⁻, which is the conjugate base of HF.
- When H₂O accepts a proton, it becomes H₃O⁺, which is the conjugate acid of H₂O.
Now we can match these to the multiple-choice options:
- HF and H₃O⁺: These are not a conjugate acid-base pair because HF is the acid and H₃O⁺ is the conjugate acid of H₂O, not related directly as conjugate pairs.
- HF and F⁻: Correct. HF is the acid and F⁻ is its conjugate base.
- H₂O and HF: These are not a conjugate acid-base pair because H₂O is the base and HF is the acid.
- H₂O and F⁻: These are not a conjugate acid-base pair because H₂O is the base and F⁻ is the conjugate base of HF, they are related but not a direct acid-conjugate base pair.
Given these points, the correct conjugate acid-base pair is:
[tex]\[
\boxed{\text{HF and } F^-}
\][/tex]
