We all have heard about “Laughing Gas” many times. But have we ever tried to know more about this gas that can make humans laugh? I guess no!
After gaining some knowledge about laughing gas, I decided to share it with you, so that next time we can laugh with knowledge!!
N2O or nitrous oxide is commonly known as laughing gas. There are several other names by which this compound is known like sweet air, protoxide of nitrogen, etc.
N2O is a colorless gas with a molecular weight of 44.013 g/mol. The boiling point of this compound is -88.48℃ and the melting point is -90.86℃.
Nitrous oxide, from being used as an oxidizer in a rocket motor to its usage in internal combustion engines, has immense use in different fields. It is also used in aerosol propellants.
Let us now move on to the preparation of this compound.
N2O Preparation Methods
Nitrous oxide can be prepared in more than one way. Some of the ways are:-
Industrial methods:- On an industrial scale, heating of ammonium nitrate gives us nitrous oxide and water vapor.
NH4NO3 ——–> 2H2O + N2O
Laboratory methods:- Preparation of nitrous oxide can be done in the lab as well. Heating the mixture of sodium nitrate and ammonium sulfate gives us N2O
2 NaNO3 + (NH4)2SO4 ——-> Na2SO4 + 2N2O + 4 H2O
Also, nitrous oxide can be formed by reacting urea, nitric acid, and sulfuric acid,
2 (NH2)2CO + 2 HNO3 + H2SO4 → 2 N2O + 2 CO2 + (NH4)2SO4 + 2H2O
Ostwald process:- Oxidation of ammonia with manganese dioxide and with bismuth oxide as catalyst gives us nitrous oxide.
This process is known as the Ostwald process.
2NH3 + 2O2 ——> N2O + 3H2O
There are many more reactions that are used for the preparation of N2O. Along with these, nitrous oxide is also a major component of the earth’s atmosphere. The concentration is 0.330 ppm.
Moreover, nitrification and denitrification are two biological or natural processes that can produce nitrous oxide.
Now to understand every other reaction involving N2O, we need to know about its lewis structure, hybridization, and bonding.
So let’s move on to these parts one by one in detail.
N2O Lewis Structure
Before going into the lewis structure of nitrous oxide, it’s better to know the steps to draw a lewis structure.
How to draw a lewis structure
A lewis structure helps us to find out about the structure of the compound, types, and the number of bonds, physical properties, and how the compound interacts with other compounds.
Drawing a lewis structure is pretty simple!
There is a common way by which we can draw the lewis structure of any compound. Have a look at the steps jotted down below:-
- Calculate the total number of valence electrons in the molecule. Do take care of +, – signs while calculating.
- Choose a central atom; generally the atom with the highest bonding sites.
- Draw a skeletal structure with single bonds only.
- Fillup the octet of the atoms with the remaining electrons. Keep in mind to start with the electronegative atoms and proceed to the electropositive one.
- Give multiple bonds if required for fulfilling the octet of the atoms.
- At last, make sure all the atoms are having their lowest possible formal charge. You can calculate the same with the formula given below:-
Now let’s find out the lewis structure of N2O,
The valence electrons of the atoms are:-
- Nitrogen = 5
- 2* Nitrogen = 5*2 = 10
- Oxygen = 6
- Total valence electrons = 16
Next, we need to decide on the central atom. In this case, nitrogen with the highest bonding sites is the central atom. So one of the nitrogen is the middle atom.
After this, we need to draw the sketch of the molecule with only single bonds. The following image attached can explain this more clearly,
We can see after drawing the sketch, remaining electrons are given around the atoms surrounding ( Structure 1). Here, the octet of the middle nitrogen is not fulfilled.
So in structure 2, one of the lone pairs of the side nitrogen is turned into a bonding pair of the middle nitrogen.
But still, there is a lack of 2 electrons, for which another lone pair is converted into a bond pair.
Thus structure 3 is the final lewis structure of nitrous oxide.
As mentioned in the rules, we can see all the atoms in the final lewis structure have their lowest formal charge. Note that, other two structures didn’t have their atoms with the lowest possible formal charge.
Now let’s move to the molecular geometry of nitrous oxide!
N2O Molecular Geometry
The molecular geometry of N2O is linear.
Molecular geometry can be determined from the VSEPR chart. N2O is similar to CO2. It has two surrounding atoms and no lone pair.
Thus this compound is an AX2 type molecule.
So we can see it has linear molecular geometry and linear electron geometry as well.
There can be confusion regarding electron geometry and molecular geometry. Let’s clear that out!
A molecular geometry includes only the atoms whereas electron geometry includes all electron pairs while determining the structure.
In more simple words, lone pairs are included in electron geometry and not in molecular geometry.
Although the shape of the N2O molecule is linear, the sharing of electrons between the atoms is unequal. The charge intensity at not uniform across the molecule.
As a result, it results in a net dipole moment and is considered a polar molecule.
From this VSEPR chart, we can also determine the hybridization of any compound. Let’s move on to the next part to know more!
Both the nitrogen atoms are sp hybridized and oxygen is sp3 hybridized in N2O.
An explanation of the hybridization of N2O is that here the terminal nitrogen is connected to another nitrogen by a triple bond thus it is sp hybridized.
The same applies to the next nitrogen. The oxygen atom is connected with the nitrogen atom by a single bond and is thus Sp3 hybridized.
Along with seeing the bonds, there is another way by which hybridization can be determined.
The hybridization of any molecule can be found using a formula.
H = ½ [ V+M-C+A]
V= No. of valence electrons
M= no. of monovalent atom
C= charge of the cation
A= charge of the anion
If, H= 2 = Sp hybridization
H= 3 = Sp2 hybridization
H= 4 = Sp3 hybridization
H= 5 = Sp3d hybridization
H= 6 = Sp3d2 hybridization
This was all about the hybridization of N2O.
Now the next topic to cover is the molecular orbital diagram of nitrous oxide.
N2O Molecular Orbital Diagram
Molecular orbital diagrams say about the mixing of orbitals in a compound.
Using a MO diagram, the bond order of a compound can be determined which gives us an idea about bond length, bond stability as well.
Nitrous oxide’s MO can be drawn easily by understanding the basics.
So for that let’s have a look at the MO of NO
Here, on the left-hand side, the atomic orbital (AO) of nitrogen is shown and on the right-hand side, AO of oxygen is shown.
In the middle, it’s the molecular orbital of the compound NO.
In the case of N2O, there will be two AO’s of nitrogen on the left-hand side.
The two atomic orbitals will be placed side by side. The oxygen will remain the same in nitrous oxide as well.
And you can form the molecular orbital by combining the AOs.
So finally you can now have a bit of knowledge about the famous “laughing gas”!!
This article revolves around the basic chemistry that we should know about nitrous oxide.
There are many more reactions and deeper knowledge that you can learn smoothly after reading this writing. Hope you enjoyed the article and if you have any query, feel free to ask me anytime!