Question

consider the reaction below.
hi + h₂o → h₃o⁺ + i⁻
which is an acid-conjugate base pair?
○ hi and h₂o
○ h₂o and h₃o⁺
○ h₃o⁺ and i⁻
○ hi and i⁻

Explanation:

To identify an acid - conjugate base pair, we use the Brønsted - Lowry definition. An acid donates a proton ($\ce{H^+}$), and its conjugate base is what remains after the acid donates the proton.

• For the reaction $\ce{HI + H_{2}O

ightarrow H_{3}O^{+} + I^{-}}$:

• $\ce{HI}$ donates a proton ($\ce{H^+}$) to form $\ce{I^-}$. So $\ce{HI}$ is the acid and $\ce{I^-}$ is its conjugate base.
• $\ce{H_{2}O}$ accepts a proton to form $\ce{H_{3}O^{+}}$, so $\ce{H_{2}O}$ is the base and $\ce{H_{3}O^{+}}$ is its conjugate acid.
• Let's analyze the other options:
• $\ce{HI}$ is an acid and $\ce{H_{2}O}$ is a base, not a conjugate acid - base pair.
• $\ce{H_{2}O}$ is a base and $\ce{H_{3}O^{+}}$ is its conjugate acid, not the pair we are looking for in terms of acid - conjugate base.
• $\ce{H_{3}O^{+}}$ is an acid (conjugate acid of $\ce{H_{2}O}$) and $\ce{I^-}$ is a base (conjugate base of $\ce{HI}$), they are not a conjugate acid - base pair of the same acid - base reaction in the required sense.

Answer:

D. HI and $\ce{I^-}$