---
title: "A student compiles data for several binary compounds to investigate periodic trends in acid strength, as shown in the table below.  | Compound | Electronegativity of \\(\\text{X}\\) | \\(\\text{H}-\\text{X}\\) bond energy (\\(\\text{kJ/mol}\\)) | |—|—|—| | \\(\\text{H}_2\\text{O}\\) | \\(3.5\\) | \\(467\\) | | \\(\\text{HF}\\) | \\(4.0\\) | \\(567\\) | | \\(\\text{HCl}\\) | \\(3.0\\) | \\(431\\) |  Across Period 2, \\(\\text{HF(aq)}\\) is a stronger acid than \\(\\text{H}_2\\text{O(l)}\\), whereas down Group 17, \\(\\text{HCl(aq)}\\) is a stronger acid than \\(\\text{HF(aq)}\\). Which of the following pairs correctly identifies the dominant factor responsible for the greater acid strength of \\(\\text{HCl(aq)}\\) compared to \\(\\text{HF(aq)}\\) and the correct comparison of their acid-ionization constants, \\(K_a\\), at \\(298\\text{ K}\\)?"
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url: "https://nerd-notes.com/ubq/123826/"
date_modified: "2026-09-28T12:30:28+00:00"
---

# A student compiles data for several binary compounds to investigate periodic trends in acid strength, as shown in the table below.

| Compound | Electronegativity of \(\text{X}\) | \(\text{H}-\text{X}\) bond energy (\(\text{kJ/mol}\)) |
|—|—|—|
| \(\text{H}_2\text{O}\) | \(3.5\) | \(467\) |
| \(\text{HF}\) | \(4.0\) | \(567\) |
| \(\text{HCl}\) | \(3.0\) | \(431\) |

Across Period 2, \(\text{HF(aq)}\) is a stronger acid than \(\text{H}_2\text{O(l)}\), whereas down Group 17, \(\text{HCl(aq)}\) is a stronger acid than \(\text{HF(aq)}\). Which of the following pairs correctly identifies the dominant factor responsible for the greater acid strength of \(\text{HCl(aq)}\) compared to \(\text{HF(aq)}\) and the correct comparison of their acid-ionization constants, \(K_a\), at \(298\text{ K}\)?

A student compiles data for several binary compounds to investigate periodic trends in acid strength, as shown in the table below.

| Compound | Electronegativity of \(\text{X}\) | \(\text{H}-\text{X}\) bond energy (\(\text{kJ/mol}\)) |
|---|---|---|
| \(\text{H}_2\text{O}\) | \(3.5\) | \(467\) |
| \(\text{HF}\) | \(4.0\) | \(567\) |
| \(\text{HCl}\) | \(3.0\) | \(431\) |

Across Period 2, \(\text{HF(aq)}\) is a stronger acid than \(\text{H}_2\text{O(l)}\), whereas down Group 17, \(\text{HCl(aq)}\) is a stronger acid than \(\text{HF(aq)}\). Which of the following pairs correctly identifies the dominant factor responsible for the greater acid strength of \(\text{HCl(aq)}\) compared to \(\text{HF(aq)}\) and the correct comparison of their acid-ionization constants, \(K_a\), at \(298\text{ K}\)?

- **A.** Greater polarity of the \(\text{H}-\text{X}\) bond | \(K_a(\text{HF}) > K_a(\text{HCl})\)
- **B.** Greater polarity of the \(\text{H}-\text{X}\) bond | \(K_a(\text{HCl}) > K_a(\text{HF})\)
- **C.** Lower \(\text{H}-\text{X}\) bond energy | \(K_a(\text{HCl}) > K_a(\text{HF})\)
- **D.** Lower \(\text{H}-\text{X}\) bond energy | \(K_a(\text{HF}) > K_a(\text{HCl})\)

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123826/*