The key difference between hydrofluoric acid and hydrochloric acid is that the hydrofluoric acid is a weak acid whereas the hydrochloric acid is a strong acid. Also, the hydrofluoric acid is capable of forming hydrogen bonds while the hydrochloric acid is unable to form hydrogen bonds.
Moreover, one other important difference between hydrofluoric acid and hydrochloric acid is in their molecular structure. The hydrofluoric acid molecule has a fluoride ion whereas the hydrochloric acid molecule has a chloride ion. Further, both hydrofluoric and hydrochloric acid are proton donors. Therefore, these acid molecules can ionize in aqueous mediums releasing protons (H+). These protons cause the acidity in the aqueous medium.
CONTENTS
1. Overview and Key Difference
2. What is Hydrofluoric Acid
3. What is Hydrochloric Acid
4. Side by Side Comparison – Hydrofluoric Acid vs Hydrochloric Acid in Tabular Form
5. Summary
What is Hydrofluoric Acid?
Hydrofluoric acid is hydrogen fluoride in water. Hydrogen fluoride is an acidic compound having the chemical formula HF and molar mass 20 g/mol. Furthermore, this acid is a starting compound for almost all the fluorine-containing compounds. Ex: Teflon. This acid is highly reactive with glass and moderately reactive with metals. Therefore, it is stored in plastic containers. However, a container made of Teflon is slightly permeable to this acid.
Figure 01: A Bottle of Hydrofluoric Acid
Hydrofluoric acid is a weak acid. That is because it has a lower dissociation constant. The dissociation of this acid gives hydronium ions (combination of protons and water molecules form hydronium ions) and fluoride ions. Among the hydrohalic acids, this is the only weak acid. We can obtain this acid via the addition of concentrated sulfuric acid to the mineral fluorite (CaF2).
What is Hydrochloric Acid?
Hydrochloric acid is an aqueous hydrogen chloride. Hydrogen chloride has the chemical formula HCl, and its molar mass is 36.5 g/mol. This acid has a pungent odor. Moreover, it is important as a starting compound for many inorganic chemicals such as vinyl chloride.
Figure 02: A Bottle of Hydrochloric Acid
Unlike HF, HCl is a strong acid that can completely ionize in the aqueous medium, forming hydronium ions and chloride ions. Thus, this acid has a high Ka value. We can prepare this acid by treating HCl with water.
What is the Difference Between Hydrofluoric Acid and Hydrochloric Acid?
Hydrofluoric acid is hydrogen fluoride in water. It is a weak acid, and it can form hydrogen bonds. Hydrochloric acid is aqueous hydrogen chloride. It is a strong acid, and it cannot form hydrogen bonds. This is the main difference between hydrofluoric acid and hydrochloric acid.
Further, the hydrofluoric acid molecule has a fluoride ion whereas the hydrochloric acid molecule has a chloride ion. However, both these are hydrohalic acids that have a hydrogen atom bonded to a halogen. Moreover, the hydrofluoric acid is the only weak acid among other hydrohalic acids.
Summary – Hydrofluoric Acid vs Hydrochloric Acid
Hydrofluoric and hydrochloric acid are hydrohalic acids because both these acid compounds have a halide bound to a hydrogen atom. Moreover, there are many differences between these two acids. The difference between hydrofluoric acid and hydrochloric acid is that the hydrofluoric acid is a weak acid and it can form hydrogen bonds whereas the hydrochloric acid is a strong acid and it is not capable of forming hydrogen bonds.
Reference:
1. “Hydrofluoric Acid.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine. Available here
2. “Hydrochloric Acid.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine. Available here
Image Courtesy:
1.’Hydrogen fluoride’By User:Dorgan – Self-photographed, (CC BY-SA 3.0) via Commons Wikimedia
2.’Hydrochloric acid 05′ (Public Domain) via Commons Wikimedia