The chemical compound responsible for keeping our swimming pools clean and safe is hypochlorous acid. Its chemical formula is HClO.
In this lesson, we will learn about HClO and how to draw its Lewis structure.
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Bleach is something we probably keep in our cleaning supplies closet in our homes. We bring the bleach out not only to clean various surfaces in our house, but also to disinfect these surfaces. The chemical compound present in bleach that is responsible for killing various bacteria and viruses is called hypochlorous acid.
Hypochlorous acid has a chemical formula of HClO, so it has one hydrogen (H) atom, one chlorine (Cl) atom and one oxygen (O) atom. Hypochlorous acid is a compound that is unstable in its pure form, so it always has to exist in solution. This means it has to exist in a solution with water as a solvent. Hypochlorous acid is a weak acid and an oxoacid because it is an acid that contains oxygen. It is formed when chlorine Cl2 is dissolved in water H2O. The chemical equation for this is shown here:
Hypochlorous acid is formed when chlorine is added to water
First, we need to count the valence electrons of hydrogen (H), chlorine (Cl) and oxygen (O). Hydrogen has one valence electron, chlorine has seven and oxygen has six.
Then we add all the electrons together. Here, the total is 14 valence electrons.
Count the total number of valence electrons in HClO.
Now, we decide how hydrogen, chlorine and oxygen are bonded together. Which one is the central atom? To make that determination, keep in mind the following rules:
- Hydrogen is never the central atom
- In general, the least electronegative atom should be the central atom
- In oxoacids, the hydrogen must be bonded to the oxygen atom
Since hypochlorous acid is an oxoacid, we know that hydrogen can’t be the central atom and it must be bonded to oxygen. So, the central atom must be oxygen. The placement of the atoms in the Lewis structure looks like this:
Step 2: Oxygen is the central atom because in oxoacids, H is bonded to O and H is never the central atom.
The next thing to do is to insert pairs of electrons between the atoms. In hypochlorous acid, there are 14 valence electrons, so, if we add the electrons (shown here as green dots) in between each atom, we have 10 electrons left.
Step 3: Insert electron pairs between the atoms.
We know that we have 10 electrons left, so we need to put the remaining 10 electrons around the atoms. How do we know how many should be around each atom? Well, except for hydrogen (H), which should contain only two valence electrons, the other atoms should contain eight valence electrons, also known as an octet of electrons.When we carry out this step, we distribute the remaining electrons (shown as red dots in the illustration) around oxygen and chlorine. The structure will now look like this:
Step 4: Distribute remaining electrons around atoms except hydrogen.
A line between atoms represent one pair of bonding electrons .
To ensure that the structure is correct, we must calculate the formal charge of each atom and make sure that the total of the formal charges for all atoms is zero. The formula for calculating the formal charge is:
Formal Charge Formula
In this diagram, the bonding electrons are the green lines and one line represents two bonding electrons.
The nonbonding electrons are the red dots, since these electrons are not involved with the bonding between atoms. We can now calculate the formal charge of each atom:
Step 5: Calculate the formal charges of each atom and add them together.
Lewis Structure of Hypochlorous Acid
In the Lewis structure, we see that hypochlorous acid has 14 valence electrons. Four are used as bonding electrons, and the remaining 10 are nonbonding electrons on oxygen and chlorine.
Hypochlorous acid is used as a disinfectant in household products like bleach, laundry detergent, and chemicals used for cleaning swimming pools.
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