Carbon Monoxide Formula is the simplest formula one can remember. Carbon monoxide (CO) is a gas made up of carbon and oxygen. It’s a combustible gas that’s colourless, odourless, and tasteless. It has a little lower density than air.

We all know that Carbon and Oxygen combine to form two gases (\({{\rm{C}}{{\rm{O}}_2}}\) and \({{\rm{CO}}}\)). When there is complete combustion of Carbon, i.e. in the presence of air, the product is mainly carbon dioxide \({\left( {{\rm{C}}{{\rm{O}}_2}} \right)}\) whereas when there is incomplete combustion of Carbon, i.e. in a limited supply of air, only half as much Oxygen adds to the Carbon, and carbon monoxide \({\left( {{\rm{CO}}} \right)}\) is formed. 

Carbon Monoxide Formula

The formula of carbon monoxide consists of one carbon atom and one oxygen atom triply bonded to each other. Hence, its formula is \({{\rm{CO}}}\).

Carbon Monoxide Molar Mass

The molecular mass of carbon monoxide, \({\rm{CO}} = \) Atomic mass of Carbon \(+\) Atomic mass of Oxygen \(= 12.01\,{\rm{u}} + 15.99\,{\rm{u}} = 28.01\,{\rm{u}}\)

Hence, one mole of carbon monoxide weighs \(28.01\;{\rm{g}}\).

Carbon Monoxide Bonding, Structure and Geometry

Carbon monoxide, \({{\rm{CO}}}\), is a toxic gas released as a byproduct during the burning of fossil fuels.  The bonding between the \({{\rm{C}}}\) atom and the \({{\rm{O}}}\) atom is of coordinate covalent type, as shown below.

In the above figure, a double bond is formed between the two atoms, with each atom providing one of the electrons to each bond. Though the oxygen atom has a stable octet configuration, the carbon atom only has six electrons and has an incomplete octet configuration. Therefore, the oxygen atom contributes one of its lone pairs to the bonding and forms a triple covalent bond.

However, one of the bonds is a coordinate covalent bond, in which one of the atoms contributes both of the electrons in the shared pair.

Once a coordinate covalent bond is formed, there lies no difference between the regular bonds and the coordinate covalent bond.

Lewis Structure of Carbon Monoxide

Lewis structure or electron dot structure is a two-dimensional representation of the valence electrons present around an atom in a molecule. It uses dots for electrons and a single line for depicting bonds between atoms.

There are \(4\) valence electrons of the carbon atom and six valence electrons of the oxygen atom in Carbon monoxide. Hence, in total, \(10\) valence electrons are distributed as follows.

Hybridisation of Carbon Monoxide

The hybridisation of Carbon in \({{\rm{CO}}}\) (Carbon Monoxide) is \({\rm{sp}}\).

It can simply be found out by its Lewis Structure in which there is a triple bond between the carbon and oxygen atom with one lone pair on each atom.

Thus, Steric No. \(= 1\) (sigma bond) \(+ 1\) (lone pair) \(= 2\).

This shows \({\rm{sp}}\) hybridisation in \({{\rm{CO}}}\).

1. A triple bond contains one \(\sigma \) and two \(\pi \) bonds, hence, there is one sigma \((\sigma )\) bond and two pi \((\pi )\) bonds between \({{\rm{C}}}\) and \({{\rm{O}}}\).
2. The σ bond is made via a \({\rm{C}}2{\rm{pz}} – {\rm{O}}2{\rm{pz}}\) head-on overlap.
3. The first \(\pi \) bond occurs through a lateral overlap of \({\rm{C}}2{\rm{px}} – {\rm{O}}2{\rm{px}}\) orbitals.
4. The second \(\pi \) bond occurs through a lateral overlap of \({\rm{C}}2{\rm{py}} – {\rm{O}}2{\rm{py}}\) orbitals

Bond Angle and Dipole Moment of Carbon Monoxide

Carbon Monoxide is a diatomic molecule with a triple bond between \({{\rm{C}}}\) and \({{\rm{O}}}\) and one lone pair of electrons on each atom. And since it only has two atoms, it has a linear molecular geometry with a bond angle of \(180\) degrees. Carbon and Oxygen forms one sigma bond and two pi bonds.

One of the triple bonds between \({{\rm{CO}}}\) is a coordinate covalent bond or dative bond. Hence, four of the shared electrons come from the oxygen atom and only two from Carbon. The formation of the dative bond causes a \({\rm{C}} \leftarrow {\rm{O}}\) polarisation of the molecule, with a slight negative charge on the carbon atom and a small positive charge on the oxygen atom. In the carbon monoxide molecule, a net negative charge \({{\rm{\delta }}^ – }\) remains at the carbon end, and the molecule has a small dipole moment of \(0.122\) Debye.

The electronegativity difference between Carbon and Oxygen is high, but the dipole moment of \({{\rm{CO}}}\) is quite low. This can be accounted for from the resonance structure of the \({{\rm{CO}}}\) molecule shown below. It can be seen that Carbon has a \(\left( { – 1} \right)\) formal charge and Oxygen has a \(\left( { + 1} \right)\). The resonance structure reduces the unfavourable charge distribution on the molecule and hence lowers the dipole moment.

The most common source of carbon monoxide is thermal combustion. Carbon monoxide is produced from the partial oxidation of carbon-containing compounds which takes place due to a limited supply of air.

Laboratory Preparation of Carbon Monoxide

The laboratory preparation of Carbon Monoxide is explained below:

Preparation of Carbon Monoxide From Carbon

When carbon dioxide gas is passed over heated charcoal, it forms carbon monoxide.

\({\rm{C}}{{\rm{O}}_2}({\rm{g}}) + {\rm{C}}({\rm{s}}) \to 2{\rm{CO}}({\rm{g}})\)

The unreacted carbon dioxide is removed by reacting it with an aqueous solution of sodium hydroxide.

\(2{\rm{NaOH}}({\rm{aq}}) + {\rm{C}}{{\rm{O}}_2}({\rm{g}}) \to {\rm{N}}{{\rm{a}}_2}{\rm{C}}{{\rm{O}}_3}({\rm{aq}}) + {{\rm{H}}_2}{\rm{O}}({\rm{l}})\)

Preparation of Carbon Monoxide From Methanoic Acid

By the dehydration of methanoic acid using conc. \({{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}\).

\({\rm{HCOOH}}({\rm{aq}}) \to {\rm{CO}}({\rm{g}}) + {{\rm{H}}_2}{\rm{O}}({\rm{l}})\)

The carbon monoxide that evolves is heavier than water and collected underwater.

Preparation of Carbon Monoxide From zinc metal

Heating a mixture of powdered zinc metal and calcium carbonate releases \({\rm{CO}}\) and leaves behind zinc oxide and calcium oxide.

\({\rm{Zn}} + {\rm{CaC}}{{\rm{O}}_3} \to {\rm{ZnO}} + {\rm{CaO}} + {\rm{CO}}\)

Preparation of Carbon Monoxide From Iodoform

Silver nitrate and iodoform react to liberate carbon monoxide.

\({\rm{CH}}{{\rm{I}}_3} + 3{\rm{AgN}}{{\rm{O}}_3} + {{\rm{H}}_2}{\rm{O}} \to 3{\rm{HN}}{{\rm{O}}_3} + {\rm{CO}} + 3{\rm{AgI}}\)

Preparation of Carbon Monoxide From metal oxalate salts

Metal oxalate salts release \({\rm{CO}}\) upon heating, leaving a carbonate byproduct.

\({\rm{N}}{{\rm{a}}_2}{{\rm{C}}_2}{{\rm{O}}_4} \to {\rm{N}}{{\rm{a}}_2}{\rm{C}}{{\rm{O}}_3} + {\rm{CO}}\)

Industrial Preparation of Carbon Monoxide

The industrial preparation of Carbon monoxide is explained below:

Preparation of Carbon Monoxide From Carbon Dioxide

In an oven, the air is passed through a bed of coke to produce \({\rm{C}}{{\rm{O}}_2}\). This \({\rm{C}}{{\rm{O}}_2}\) equilibrates with the remaining hot Carbon to give \({\rm{CO}}\). Above \(800\,^\circ {\rm{C}},{\mkern 1mu} {\rm{CO}}\) is the predominant product.

\({\rm{C}}{{\rm{O}}_2} + {\rm{C}} \to 2{\rm{CO}}\left( {\Delta {\rm{H}} = 170\frac{{{\rm{kJ}}}}{{{\rm{mol}}}}} \right)\)

Preparation of Carbon Monoxide From Water

An endothermic reaction of steam and Carbon produces a mixture of hydrogen and carbon monoxide(Water-gas).

\({{\rm{H}}_2}{\rm{O}} + {\rm{C}} \to {{\rm{H}}_2} + {\rm{CO}}\left( {\Delta {\rm{H}} = + 131\frac{{{\rm{kJ}}}}{{{\rm{mol}}}}} \right)\)

By the direct oxidation of Carbon in a limited supply of Oxygen or air.

\(2{\rm{C}}({\rm{s}}) + {{\rm{O}}_2} \to 2{\rm{CO}}({\rm{g}})\)

By the reduction of metal oxide ores with Carbon

\({\rm{MO}} + {\rm{C}} \to {\rm{M}} + {\rm{CO}}\)

Physical Properties

1. Carbon monoxide is a toxic, colourless, odourless and tasteless gas.
2. It supports combustion and burns with a pale blue flame.
3. It becomes a liquid at \(81.62\;{\rm{K}}\left( { – 191.53\,^\circ {\rm{C}}} \right)\) and is insoluble in water above \(70\,^\circ {\rm{C}}.\)
4. Its Melting point is \(- 205\,^\circ {\rm{C}},\) and the Boiling point is \(- 191.5\,^\circ {\rm{C}}.\)
5. The Density of carbon monoxide gas at \(25\,^\circ {\rm{C}}\) is \(1.145\;{\rm{g}}/{\rm{L}}.\)

Chemical Properties

Carbon monoxide is a strong reducing agent and reduces metal oxides for metals less reactive than Carbon. For example- haematite ( iron\(\left( {{\rm{III}}} \right)\)oxide \({{\rm{F}}{{\rm{e}}_2}{{\rm{O}}_3}}\)) is reduced to iron in the blast furnace.

\({\rm{F}}{{\rm{e}}_2}{{\rm{O}}_3}(\;{\rm{s}}) + 3{\rm{CO}}({\rm{g}}) \to 2{\rm{Fe}}({\rm{l}}) + 3{\rm{C}}{{\rm{O}}_2}(\;{\rm{g}})\)

Affinity for Transition Metals

Carbon monoxide does not show acidic or basic properties. However, it has a strong affinity for transition metals (located between Groups \(2\) and \(3\) of the Periodic Table). It acts as a ligand towards the transition metal through the lone pair on the carbon atom. For example, tetracarbonyl nickel \({\rm{Ni}}{({\rm{CO}})_4}\) is prepared by the reaction of nickel with carbon monoxide.

\({\rm{Ni}}({\rm{s}}) + 4{\rm{CO}}({\rm{g}}) \to {\rm{Ni}}{({\rm{CO}})_4}\)

Carbon monoxide is so reactive with nickel that it will have etched the surface within a couple of minutes.

Carbon Monoxide Toxicity

Carbon monoxide is a very poisonous gas. Its toxicity arises from its ability to bind to transition metals such as the iron found at the centre of a haem molecule. Carbon monoxide is attracted to haemoglobin over \(200\) times more strongly than oxygen. Therefore, in the blood, the presence of carbon monoxide prevents some of the haemoglobin found in red blood cells from carrying sufficient oxygen.

Symptoms of carbon monoxide poisoning are dizziness and headaches. Carbon monoxide poisoning can be recognised, as victims will often have unnaturally bright red lips.

Uses of Carbon Monoxide

1. In the form of producer gas or water gas, it is widely used as a fuel in industrial operations.
2. The gas is also an effective reducing agent and is used in the extraction of metals. For example, when carbon monoxide is passed over hot iron oxides, the oxides are reduced to metallic iron, while the carbon monoxide is oxidised to carbon dioxide
3. It is used in the Mond process of separating nickel.
4. It is used in the manufacture of hydrocarbons and their oxygen derivatives.
5. Carbon monoxide also reacts with certain metals, especially iron, cobalt, and nickel, to form compounds known as carbonyls.

Summary

Carbon monoxide is a common pollutant produced when hydrocarbon fuels (natural gas, petrol, diesel) are burned. The relative amount of \({\rm{CO}}\) produced accounts for the efficiency of combustion. Its ability to act as a reducing agent helps in metallurgical processes. Hence, it’s important to know its structure and properties. In this article, we learned the formula, structure and properties of carbon monoxide. We also learnt its preparation as well as its uses.

FAQs

Q.1. Is \({\rm{C}}{{\rm{O}}_2}\) same as \({\rm{CO}}\)?
Ans: No \({\rm{C}}{{\rm{O}}_2}\) is not as same as \({\rm{CO}}\) because \({\rm{C}}{{\rm{O}}_2}\) stands for carbon dioxide, whereas \({\rm{CO}}\) stands for carbon monoxide.

Q.2. Which is worse, carbon dioxide or carbon monoxide?
Ans: Carbon monoxide is far more dangerous than carbon dioxide. This is because carbon monoxide has a great affinity towards transition metals. It readily combines with iron present in haemoglobin to form carboxyhaemoglobin, which reduces the blood’s oxygen carrying capacity.

Q.3. What level of carbon monoxide is dangerous?
Ans: At concentrations above \(150\) to \(200\,{\rm{ ppm}}\), carbon monoxide is dangerous. It causes disorientation, unconsciousness and may be fatal at times.

Q.4. What creates carbon monoxide in a home?
Ans: Household appliances, such as boilers, central heating systems, water heaters, cookers, and open fires which use gas, oil, coal and wood may be possible sources of \({\rm{CO}}\) gas. Burning charcoal produces \({\rm{CO}}\) gas, and blocked chimneys can stop \({\rm{CO}}\) from escaping.

Q.5. What does carbon monoxide smell like?
Ans: Carbon monoxide is a gas that has no odour, colour or taste. Hence, we cannot see or smell it, but it can be very dangerous to our health and even fatal.

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