Hybridization, Molecular Geometry, and HCl Lewis Structure

Without a doubt, hydrochloric acid (HCl) is a highly strong acid. It’s a colourless, pungent-smelling acidic water containing chlorine.

The chemical formula for both hydrogen chloride and hydrochloric acid is HCl, which causes a lot of confusion. So, before moving on to a new thought, it’s critical to dispel this doubt.

The gaseous form is hydrogen chloride, whereas the aqueous form is hydrochloric acid.

Hydrochloric acid, abbreviated as HCl, is an aqueous solution of hydrogen chloride having the chemical formula HCl. Except for their bodily states, everything else is the same.

Muriatic acid is another name for hydrochloric acid, which is interesting to know.

HCl formation reaction

To make HCl, chlorine (Cl2) and hydrogen (H2) gas are mixed directly at a temperature of 250°C.

HCl Lewis Structure, Molecular Geometry, and Hybridization

HCl

Hydrochloric acid or HCl is a very strong acid without any doubt. It is a colorless, pungent-smelling, chlorine-based acid-containing water.

Very often there is confusion regarding hydrogen chloride and hydrochloric acid, as HCl is the chemical formula for both. So it’s very necessary to clear this doubt before moving on to any new concept.

Hydrogen chloride is the gaseous form whereas hydrochloric acid is the aqueous form.

In simple words, hydrochloric acid is the aqueous solution of hydrogen chloride, with the chemical formula HCl. All other things are the same except their physical states.

It’s interesting to know that another name for hydrochloric acid is muriatic acid.

Contents  show 

Formation reaction of HCl

Chlorine (Cl2) gas and hydrogen gas (H2) are directly combined rapidly above 250℃ temperature to get HCl

H2    +    Cl2    —–>     2HCl

HCl immediately decomposed into the hydronium ion (H3O+) and chloride in an aqueous solution (Cl-). As a result, hydrochloric acid is a powerful acid.

HCl    +   H2O    ——>      H3O+    +     Cl-

There are a few other HCl preparation methods besides the one stated above, such as:-

Method of organic synthesis-

R-H + Cl2     ——>    R-Cl + HCl
R-Cl + HF     ——>    R-F + HCl

HCl can be made in the laboratory by reacting sodium chloride with sulfuric acid or NaHSO4.

NaCl   +   H2SO4     —–>     NaHSO4  +   HCl
NaCl    +   NaHSO4     ——->     HCl    +   Na2SO4

Some reactive chlorine compounds, such as phosphorus chloride, thionyl chlorides, and acyl chlorides, are hydrolyzed to produce HCl as a byproduct.

PCl5    +    H2O   —->   POCl3   +    HCl

In addition to this, we must understand some fundamental aspects of HCl, such as the Lewis structure, hybridization, and so on.

So, let’s try to grasp these concepts in greater depth and learn more about this complex!

Lewis Dot Structure in HCl

It’s vital to understand the basics of the lewis structure before diving into the lewis dot structure of HCl.

Lewis structure, in simple terms, is the distribution of electrons around the atoms that allows us to determine the number and types of bonds in a chemical.

To obtain the lewis dot structure of any compound, we can follow a few simple methods.

To begin, we must add up the valence electrons of all the atoms to determine the total amount of valence electrons in the molecule.

Second, we must select a central atom, which is usually the least electronegative atom or the atom with the greatest number of accessible sites.

The skeletal structure of the molecule will be sketched in the third phase using only single bonds.

The leftover electrons following the establishment of single bonds in the skeletal structure must then be filled around the atoms to complete the octet. It’s best to begin with the electronegative atoms and work your way up to the electropositive ones.

All of the atoms’ octet compliance needs to be double-checked. If there is a mistake, we must correct it by issuing multiple bonds.

Finally, all atoms should have the lowest formal charge feasible. The following formula can be used to check it:-

Let’s move on to HCl now.

Because HCl only has two atoms, creating a Lewis dot structure for it is simple!

To begin, determine the total amount of valence electrons;

1 = Hydrogen

7 = Chlorine

a total of 8

As a halogen, chlorine requires one more electron to complete its octet.

Similarly, because hydrogen’s outermost shell can retain up to two electrons, it requires one extra electron to achieve an octet.

As a result, a single bond is established between the two atoms, resulting in the development of a covalent bond.

Molecular Geometry of HCl

HCl has a linear molecular geometry/shape and a tetrahedral electron geometry, according to VSEPR theory. The bonding angle is 180 degrees.

The VSEPR theory graphic shown above clearly illustrates that HCl is an AXE3 type molecule, where

Here, A is the core atom, while Cl is the central atom.

Here, X = atom linked to A = H.

On A = 3, E = lone pair ( Cl have 3 lone pairs)

The distinction between molecular geometry/shape and electron geometry may now be questioned. Let’s investigate these two geometries further.

When defining the geometry of a molecule, electron geometry takes into account all electron pairs.

Molecular geometry, on the other hand, solely considers the atoms.

To put it another way, lone pairs are taken into account in electron geometry but not in molecule geometry/shape.

When lone pairs of Cl are taken into account, the hydrochloric acid structure is tetrahedral. HCl takes on a linear structure when the lone pairs are ignored.

Hybridization with HCl

Because HCl is a linear diatomic molecule with a H atom and a Cl atom bound covalently, there is no hybridization. As a result, no additional stability is required.

It only has one atom as a surrounding atom because it is a diatomic molecule. As a result, there can only be one possible structure, and this molecule does not require any additional stability.

A molecule’s hybridization can be predicted using either the VSEPR theory chart or the formula;

[V+M-C+A] H = 12

Here,

H stands for hybridization.

V is the number of valence electrons.

M is the number of monovalent atoms.

C is the cation’s charge.

A is the anion’s charge.

If H= 2 = Sp hybridization, then

Sp2 hybridization = H= 3

Sp3 hybridization = H= 4

Sp3d hybridization with H=5

Sp3d2 hybridization (H=6)

We can simply detect the hybridization of any molecule with all of these!

Molecular Orbital Diagram of HCl

In simple terms, the molecular orbital theory describes how atoms in a molecule combine their atomic orbitals to generate molecular orbitals.

This theory explains how electrons are arranged in orbitals and how bond order is determined.

The molecular orbital diagram is as follows:

From the above image, we can clearly identify the atomic orbitals of H and Cl, as well as the MO of HCl.

The energy of chlorine’s 3s orbital is significantly smaller. As a result, no interaction with hydrogen’s 1s orbital is feasible.

As a result, the 3p orbital (3px, 3py, 3pz) of chlorine, which has a similar energy to the 1s orbital of hydrogen, collides with the orbital of hydrogen.

Over here, only sigma overlap is taking place. This is because, whereas the 3p orbital of Cl and the 1s orbital of H mix, their symmetry is different.

As a result, the sigma overlap is the only option.

As can be seen, HCl’s MO has six pairs of nonbonding electrons and one pair of bonding electrons in the 3pz orbital.

Because of its increased electronegativity, the sigma bond electrons will also be closer to Cl.

All of these ideas are crucial for fully comprehending the molecular orbital diagram of HCl.

HCl’s Polarity

Because chlorine has a higher electronegativity than hydrogen, the HCl molecule is polar.

The primary charge is pulled to one side by chlorine, which forms a negative pole, while hydrogen becomes a positive pole. The molecule is now classified as a polar molecule.

You should also read an article on the polarity of HCl for more details.

HCl’s Physical Properties

Let’s take a look at some of this compound’s physical features. HCl has a molar mass of 36.46 g/mol. HCl also has a low boiling point of -85.05°C and a melting point of -114.2°C.

The characteristics of HCl might change depending on its molarity.

This molecule has numerous applications, ranging from the production of polyvinyl chloride for plastic production in industries to the usage of dilute HCl as a descaling agent in homes.

In the food industry, HCl is used in the manufacturing of gelatin. It’s also utilised in food additives and leather production.

HCl is also used in the refinement of metals, the pickling of steel, the creation of organic and inorganic compounds, and ph control.

Conclusion

Despite the fact that HCl has a variety of applications, we must exercise caution when employing it. On human skin, concentrated HCl has a high corrosive action and can cause serious injury. The vapours are also hazardous, causing coughing, choking, and throat irritation.

These damages can sometimes become severe and irreversible. As a result, it’s best to use this drug with caution and vigilance.

I tried to present all of the major aspects of HCl that we need to know before diving into its interactions. I hope that was useful in some way and you learned a little more about this compound as a result of it!

Read more: What is the difference between polar and nonpolar acetone?

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.

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