Hydrochloric acid is a white liquid with a strong odour. It has the chemical formula HCl, which means it has one hydrogen atom and one chlorine atom. Muriatic acid is another name for it. Hydrochloric acid is made in the industry by reacting hydrogen chloride with water.
It’s also found in the stomachs of humans and several other animals as a component of gastric acid. It’s used to make a variety of inorganic compounds, pickle steel, adjust pH, and neutralise reactions, among other things.
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You’ll discover everything you need to know about the intermolecular forces in HCl in this article.
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In HCl, what kinds of intermolecular forces are present?
Between the molecules of HCl, there are dipole-dipole interactions and London dispersion forces.
The electronegativity difference between hydrogen (2.2) and chlorine (3.16) results in a slight positive charge on the hydrogen atom and a slight negative charge on the chlorine atom. Dipole-dipole interaction refers to the attraction forces that emerge between one molecule’s slightly positive hydrogen atom and another molecule’s slightly negative chlorine atom.
All molecules are affected by the London dispersion forces.
Why is HCl’s boiling point so low?
The hydrogen and chlorine atoms in the HCl molecule are joined by a polar covalent link. The electronegativity mismatch between hydrogen and chlorine causes two distinct poles to form inside the molecule, forming this link.
Because the chlorine atom is more electronegative, it gains a partial negative charge by attracting the shared electron pair to itself, whereas the hydrogen atom gains a partial positive charge.
As a result, two opposed charges or poles form inside the same molecule, which is known as a dipole.
Intermolecular attraction forces are created when the positively charged hydrogen end of one molecule comes into contact with the negatively charged chlorine end of another molecule, which is known as the dipole-dipole interaction.
The London dispersion force is another sort of intermolecular interaction that exists between HCl molecules. These forces exist between all molecules and aren’t particularly relevant when discussing intermolecular bonding in HCl.
As a result, the only intermolecular forces that matter between HCl molecules are dipole-dipole interactions, which are weak in compared to other forms of intermolecular forces seen in other compounds.
The following is the strength order of distinct intermolecular forces:
Dipole-Dipole > Dipole-Induced Dipole > Induced Dipole-Induced Dipole forces > Ion – Ion > Ion – Dipole > Hydrogen Bonding > Dipole-Dipole > Dipole-Induced Dipole > Induced Dipole-Induced Dipole forces
The intensity of the intermolecular forces at action in a molecule determines the boiling point of that compound. Intermolecular bonding is usually strong in ionic substances.
When we look at the HCl molecule, we can see that it is a non-ionic chemical with polar covalent bonds. In addition, dipole-dipole interactions are the only intermolecular forces at work in this molecule.
As a result, HCl has a low boiling point due to weak intermolecular interaction among its molecules.
Intermolecular Forces Types
Intermolecular forces are the forces of attraction that occur between molecules of the same chemical that are close together. Dipole-dipole interaction, hydrogen bonding, and so on.
These are distinct from intramolecular attraction forces, which exist between two or more atoms or ions in the same molecule. Ionic bonds, covalent bonds, and other types of bonds are examples.
The following are the several forms of intermolecular forces of attraction:
• Ion-ion forces: Electrostatic forces that form between the molecules of an ionic compound. The creation of ion-ion force occurs when oppositely charged ions from distinct molecules come close to each other.
• The forces that exist between a polar and an ionic molecule are known as the ion-dipole force. The atoms in a polar molecule have a partly positive and partial negative charge.
When NaCl or KCl are dissolved in water, their ions bind to the polar molecules of H2O, for example. The strength of these interactions is determined by the polar molecule’s size and dipole moment.
• Dipole-Dipole interactions: These interactions take place in polar molecules with a constant dipole moment. These compounds create dipole-dipole interactions when they interact with other molecules that are comparable to them.
The difference in electronegativity of the bound atoms determines a molecule’s polarity. In the case of HCl, for example, the hydrogen atom gains a partial positive charge while the chlorine atom gains a partial negative charge.
• Hydrogen bonding: Because of the electronegativity difference between the atoms in a molecule, hydrogen bonding can also be regarded a sort of dipole-dipole interaction.
Hydrogen bonding occurs exclusively in molecules containing hydrogen and strongly electronegative elements such as nitrogen, oxygen, and fluorine.
• Induced dipole-induced dipole forces: These are also known as London Dispersion forces. These are the tiniest intermolecular forces that exist between any two molecules.
The movement of electrons within a molecule causes induced charge, which is a momentary positive or negative charge.
Induced dipole-induced dipole interaction happens when these induced charges connect with the oppositely charged end of another molecule.
Why does hydrogen bonding not happen in HCl?
Hydrogen bonding occurs when hydrogen is covalently bound to a strongly electronegative atom such as nitrogen, oxygen, or fluorine in a molecule.
A partial positive charge develops on the hydrogen atom and a partial negative charge develops on the electronegative atom due to the huge difference in electronegativity of the atoms.
Between the hydrogen atom of one molecule and the electronegative atom of another molecule, an electrostatic attraction arises.
The strength of these attraction forces is mostly determined by the difference in electronegativity between the atoms as well as the size difference between them.
The strength of hydrogen bonding increases as the electronegativity difference between the molecules grows, but reduces as the size difference between the atoms grows.
Because the size of the fluorine, nitrogen, and oxygen atoms in HF, NH3, and H2O is quite tiny, hydrogen bonding is conceivable in these molecules.
Although the electronegativity difference is appropriate in the case of HCl, the size of the chlorine atom is relatively high, resulting in a low electron density. As a result, this molecule can’t establish intermolecular hydrogen bonds.
Is there a dipole moment in HCl?
The dipole moment of a molecule is a measurement of its net polarity. The difference in electronegativity of the joining atoms causes the polarity. As a result, as the electronegativity difference grows, so does the dipole moment of a molecule.
On the Pauling scale, the electronegativity of the hydrogen atom is 2.3, while the electronegativity of the chlorine atom is 3.16, suggesting a large electronegativity discrepancy.
As a result, the dipole moment of HCl is 1.03 Debye.
FAQs
What effect does intermolecular bonding have on the qualities of a substance?
The boiling and freezing points of a substance are affected by intermolecular forces. The boiling and freezing points of a substance usually rise in tandem with the intensity of intermolecular forces, and vice versa.
Question: Of all the hydrogen halides, why does HCl have the lowest boiling point?
Due to the presence of hydrogen bonding among its molecules, HF has the highest boiling point among hydrogen halides. HCl has a dipole-dipole interaction, however the bromine and iodine molecules are not sufficiently electronegative to polarise the molecule.
These atoms, on the other hand, have more electrons than chlorine, resulting in higher van der Waals forces. In HI, these forces are greatest, whereas in HCl, they are least.
As a result, the boiling points of hydrogen halides rise in the following order:
HCl < HBr < HI <HF
Question: Why is HCl’s melting point lower than NaCl’s?
Answer: The HCl molecule has a basic linear shape with weak intermolecular interactions connecting the molecules. Because the melting of a substance is dependent on the breaking of intermolecular interactions, HCl has no trouble doing so.
NaCl, on the other hand, is an ionic compound in which the molecules are bound together by strong ion-ion interactions. As a result, as compared to HCl, NaCl has a greater melting point.
HCl’s properties
The following are some of the most important features of hydrogen chloride:
• At room temperature and pressure, it exists as a clear gas with the chemical formula HCl.
• HCl has a molecular weight of 36.458 gm/mol.
• The melting and boiling points of HCl are affected by the aqueous solution’s concentration or molarity.
• At 189 K, HCl liquefies and at 159 K, it freezes.
• It’s a monoprotic acid that’s quite corrosive.
Conclusion
Intermolecular forces of attraction such as dipole-dipole interaction and London dispersion forces exist between the HCl molecules.
The electronegativity mismatch between the hydrogen and chlorine atoms causes the dipole-dipole interaction between HCl molecules.
The following is the strength order of distinct intermolecular forces:
Dipole-Dipole > Dipole-Induced Dipole > Induced Dipole-Induced Dipole forces > Ion – Ion > Ion – Dipole > Hydrogen Bonding > Dipole-Dipole > Dipole-Induced Dipole > Induced Dipole-Induced Dipole forces
HCl has a dipole moment of 1.03 Debye.
Good luck with your studies!!
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