Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 20: Problem 66

Explain why \(\mathrm{HF}\) is a weak acid, whereas \(\mathrm{HCl}, \mathrm{HBr}\), and \(\mathrm{HI}\) are all strong acids.

Short Answer

Expert verified
In summary, $\mathrm{HF}$ is a weak acid because fluorine is the most electronegative element, resulting in a strong bond with hydrogen, and fewer hydrogen ions released when dissolved in water. In contrast, $\mathrm{HCl}$, $\mathrm{HBr}$, and $\mathrm{HI}$ are strong acids because they have less electronegative halogen atoms, resulting in weaker bonds with hydrogen, and more hydrogen ions released when dissolved in water.

Step by step solution

01

Definition of Weak and Strong Acids

A weak acid is one that does not dissociate completely in water, meaning not all of its molecules release hydrogen ions (H+) when dissolved in it. Conversely, a strong acid completely dissociates in water, releasing a significant amount of H+ ions.
02

Acid strength and bond strength

The strength of an acid is mostly related to the strength of the bond between the hydrogen (H) atom and the other atom it's bound to, known as the conjugate base. In this case, we're comparing the bond between H and F (HF) to the bonds between H and Cl (HCl), H and Br (HBr), and H and I (HI). In general, the weaker the bond between the H atom and the conjugate base, the stronger the acid.
03

Electronegativity and bond strength

Electronegativity is the ability of an atom to attract electrons in a bond. A higher electronegativity means that the atom is more effective at attracting electrons. The bond strength between H and the conjugate base is affected by the electronegativity difference. When the electronegativity difference is large, the bond is more polar, and the bond is weaker. Conversely, when the electronegativity difference is smaller, the bond is less polar and more robust.
04

Electronegativity of halogens

The halogens (F, Cl, Br, and I) are all very electronegative, but there is a difference in their electronegativity values. Fluorine (F) is the most electronegative element with a value of 3.98, followed by chlorine (Cl: 3.16), bromine (Br: 2.96), and iodine (I: 2.66).
05

HF vs. HCl, HBr, and HI

Comparing acid strength, bond strength, and electronegativity of HF, HCl, HBr, and HI, we can see why HF is a weak acid, while the others are strong acids. Because F is the most electronegative element, it forms a very strong bond with hydrogen, meaning the bond is harder to break. Therefore, HF does not dissociate completely in water, releasing fewer H+ ions, making it a weak acid. On the other hand, HCl, HBr, and HI have less electronegative halogen atoms. This results in weaker bonds with hydrogen, which are more easily broken. Thus, these acids dissociate completely in water, releasing more H+ ions, making them strong acids.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

What ions are found in hard water? What happens when water is "softened"?

Elemental boron is produced by reduction of boron oxide with magnesium to give boron and magnesium oxide. Write a balanced equation for this reaction.

Many oxides of nitrogen have positive values for the standard free energy of formation. Using \(\mathrm{NO}\) as an example, explain why this is the case.

Write a balanced equation describing the reduction of \(\mathrm{H}_{2} \mathrm{SeO}_{4}\) by \(\mathrm{SO}_{2}\) to produce selenium.

From the information on the temperature stability of white and gray tin given in this chapter, which form would you expect to have the more ordered structure (have the smaller positional probability)?
See all solutions

Recommended explanations on Chemistry Textbooks

Making Measurements

Read Explanation

Inorganic Chemistry

Read Explanation

Kinetics

Read Explanation

Chemistry Branches

Read Explanation

The Earths Atmosphere

Read Explanation

Chemical Reactions

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free