It is also found as a component of gastric acid in the stomach of humans as well as some other animals. It is used in the production of a number of inorganic compounds, in the pickling of steel, in pH control and neutralization reactions, etc. Hey Readers!!! Welcome to another fresh article on techiescientist. In this article, you will learn everything you need to know about the intermolecular forces in HCl. So keep reading…. What types of intermolecular forces are present in HCl? HCl has the dipole-dipole interaction and London dispersion forces present in between its molecules. Due to the electronegativity difference between hydrogen (2.2) and chlorine (3.16), a slight positive charge develops on the hydrogen atom while the chlorine atom acquires a slight negative charge. The attraction forces that arise between the slightly positive hydrogen atom of one molecule and the slightly negative chlorine atom of another molecule are known as dipole-dipole interaction. The London dispersion forces occur amongst all the molecules.
Why does HCl have a low boiling point?
In the HCl molecule, the hydrogen atom and the chlorine atom are bonded through a polar covalent bond. This bond is formed owing to the electronegativity difference between hydrogen and chlorine due to which two separate poles develop inside the molecule. The chlorine atom being more electronegative acquires a partial negative charge by pulling the shared electron pair towards itself while the hydrogen atom attains a partial positive charge. Therefore, two opposite charges or poles develop inside the same molecule that is also referred to as a dipole. As the positively charged hydrogen end of one molecule comes in contact with the negatively charged chlorine end of another molecule, intermolecular attraction forces come into the picture, which is known as the dipole-dipole interaction. The other type of intermolecular force present between HCl molecules is the London dispersion force. These forces actually exist between all the molecules and are not of much importance while we talk about intermolecular bonding in HCl. Hence, the only relevant intermolecular forces between HCl molecules are the dipole-dipole interactions which are quite weak in strength in comparison to other types of intermolecular forces present in various other compounds. The order of the strength of different intermolecular forces is as follows: Ion – Ion > Ion – Dipole > Hydrogen Bonding > Dipole-Dipole > Dipole-Induced Dipole > Induced Dipole-Induced Dipole forces The boiling point of a compound depends upon the strength of the intermolecular forces working in that compound. Mostly, ionic compounds have strong intermolecular bonding. Looking at the HCl molecule, it is a non-ionic compound bonded through polar covalent bonding. Also, the only intermolecular forces acting in this compound are dipole-dipole interactions. Therefore, owing to weak intermolecular bonding amongst its molecules, HCl has a low boiling point.
Types of Intermolecular Forces
The intermolecular forces refer to the forces of attraction that exist between the different molecules of the same compound that are placed in close proximity with each other. For example, dipole-dipole interaction, hydrogen bonding, etc. These are different from the intramolecular forces of attraction that exist between the two or more atoms or ions of the same molecule. For example, ionic bonds, covalent bonds, etc. The different types of intermolecular forces of attraction are described below: • Ion-ion forces: These are the electrostatic forces that develop between the molecules of an ionic compound. When the oppositely charged ions of different molecules come close to each other, they result in the development of ion-ion force. • Ion-dipole force: These are the forces that exist between a polar and an ionic molecule. The polar molecule has a partial positive and a partial negative charge on its atoms.
For example, when NaCl or KCl is dissolved in water, their ions associate with the polar molecules of H2O. The strength of these interactions depends upon the size as well as the dipole moment of the polar molecule. • Dipole-Dipole interaction: These interactions occur in the polar molecules which have a permanent dipole moment. When these molecules interact with other similar molecules, they form dipole-dipole interaction. The polarity of a molecule is due to the difference in the electronegativity of the bonded atoms. For example, in the case of HCl, hydrogen atom acquires partial positive charge while partial negative charge develops on chlorine atom.
• Hydrogen bonding: This can also be considered a type of dipole-dipole interaction as they arise owing to the electronegativity difference between the atoms of a molecule. Specifically, hydrogen bonding only occurs in the molecules where hydrogen is bonded with highly electronegative atoms like nitrogen, oxygen, and fluorine. Check out the below articles CH3OH Intermolecular Forces
• London Dispersion forces: These are also known as induced dipole-induced dipole forces. These are the weakest type of intermolecular forces that exist between all types of molecules. As the electrons inside a molecule move, a temporary positive or negative charge develops, which is also referred to as induced charge. These induced charges when interacting with the oppositely charged end of another molecule, induced dipole-induced dipole interaction occurs. Check out the article on CH4 Intermolecular Forces.
Why Hydrogen Bonding does not occur in HCl?
Hydrogen bonding exists between the molecules in which hydrogen is covalently bonded with a highly electronegative atom such as nitrogen, oxygen, and fluorine. Due to the large difference in the electronegativity of the atoms partial positive charge develops on the hydrogen atom and partial negative charge develops on the electronegative atom. The electrostatic attraction develops between the hydrogen atom of one molecule and the electronegative atom of another molecule. The strength of these attraction forces majorly depends upon the electronegativity difference between the atoms as well as on the size difference between the atoms. The strength of hydrogen bonding increases with an increase in the electronegativity difference between the molecules and decreases with the increase in the size difference of the atoms. For example, in the case of HF, NH3, or H2O, the size of fluorine, nitrogen, and oxygen atom is relatively small due to which hydrogen bonding is possible in these molecules. However, in the case of HCl, although, the electronegativity difference is apt, the size of the chlorine atom is quite large due to which the electron density is low. Hence, this molecule is unable to form intermolecular hydrogen bonding.
Does HCl have a dipole moment?
The measure of the net polarity of a molecule is known as its dipole moment. The polarity arises due to the difference in the electronegativity of the combining atoms. Hence, the dipole moment of a molecule also increases as the electronegativity difference increases. The value of electronegativity for the hydrogen atom is 2.3 while for the chlorine atom is 3.16 on the Pauling scale, indicating a high electronegativity difference. Therefore, HCl has a dipole moment of 1.03 Debye.
Question: What is the impact of intermolecular bonding on the properties of a substance? Answer: The intermolecular forces affect the boiling and freezing point of a substance. Usually, the boiling as well as the freezing point of a substance increases as the strength of intermolecular forces increases, and vice versa. Question: Why does HCl have the lowest boiling point amongst all hydrogen halides? Answer: Amongst hydrogen halides, HF has the highest boiling point owing to the presence of hydrogen bonding amongst its molecules. In other hydrogen halides, HCl contains dipole-dipole interaction while the bromine and iodine molecules are not that electronegative as to polarize the molecule. However, the number of electrons in these atoms is more than chlorine due to which they exhibit stronger van der Waals forces. These forces are highest in HI and lowest in HCl. Therefore, amongst hydrogen halides the boiling points increase in the following order: HCl < HBr < HI <HF Question: Why does HCl have a lower melting point than NaCl? Answer: The HCl molecule has a simple linear structure and the molecules are linked through weak intermolecular forces. As the melting of a substance depends upon the breaking of the intermolecular forces it is quite easy for HCl to overcome them. However, NaCl is an ionic compound in which the molecules are held together through ion-ion interactions that are quite strong. Therefore, NaCl has a higher melting point in comparison to HCl. Related Topics Does NH3 have hydrogen bonding Is HCl Polar or Nonpolar Is HCl Ionic or Covalent HCl Lewis Structure, Geometry, Hybridization, and Polarity pH of HCl Is HBr Polar or Nonpolar Is HF Polar or Nonpolar Is HF Ionic or Covalent
Properties of HCl
A few important properties of hydrogen chloride are as follows: • It occurs as a transparent gas at room temperature and pressure, denoted by the chemical formula HCl. • The molecular weight of HCl is 36.458 gm/mol. • The melting and boiling points of HCl depend upon the concentration or molarity of the aqueous solution. • HCl liquefies at 189 K and freezes at 159 K temperature. • It is a highly corrosive, monoprotic acid.
Conclusion
Dipole-dipole interaction and London dispersion forces are present in between the HCl molecules as intermolecular forces of attraction. The dipole-dipole interaction between HCl molecules arises owing to the electronegativity difference between the hydrogen and chlorine atom. The order of the strength of different intermolecular forces is as follows: Ion – Ion > Ion – Dipole > Hydrogen Bonding > Dipole-Dipole > Dipole-Induced Dipole > Induced Dipole-Induced Dipole forces The dipole moment of HCl is 1.03 Debye. Happy Learning!!
