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Molar Mass Of CO2 (Carbon Dioxide)

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Carbon dioxide is a covalent compound composed out of two oxygen atoms double bonded to a carbon atom. At room temperatures, carbon dioxide is a colorless odorless gas that is 60% denser than normal air. Carbon dioxide is a natural byproduct of the cellular respiration cycle in animals and one of the main reactants processed during plant photosynthesis. Carbon dioxide is also a naturally occurring greenhouse gas in the Earth’s atmosphere and is formed via the activity of volcanoes, hot springs, animal respiration, fire, and geological movement.

The chemical formula of carbon dioxide is CO2. The entire molar mass of carbon dioxide can be determined by adding together the molar masses of its atomic components. Carbon has a molar mass of 12.0107 g/mol and oxygen has a molar mass of 15.9994 g/mol. Multiplying these values to reflect the proportions in a single molecule of carbon dioxide gives us:

12.0107+15.9994(2) = 44.01 g/mol

So, the molar mass of carbon dioxide is 44.01 g/mol.

Molar Mass In a Nutshell

The molar mass of a substance tells you how much one mole of that substances weighs. A ‘mole” is a counting number that corresponds to the number 6.023 × 1023. Just like the words “million” and “billion”, a “mole” specifies a particular quantity of something. One mole of apples would be 6.023 × 1023 apples. Likewise, one mole of a substance would have 6.023 × 1023 constituent particles. So the molar mass is a measurement that tells you how much 6.023 × 1023 atoms or molecules of a substance weighs.


The mole is also called Avogadro’s number, after Italian chemist Amedeo Avogadro. Credit: WikiCommons CC0 1.0

Every element has a standard atomic weight—a weighted average of all the weights of the different isotopes of an element. The molar mass of an element can be determined by multiplying the standard atomic weight by the molar mass constant Mμ=1g/mol. The standard atomic weight can be found on the periodic table under the corresponding element. For example, arsenic (As) has a standard atomic weight of 74.9216. Multiplying this value by the molar mass constant tells us that arsenic has a molar mass of 74.9216 g/mol. 6.023 × 1023 atoms of arsenic would weigh 74.9216 grams.

The molar mass of an entire compound is simply equal to the sum of the molar masses of its constituent elements. Let’s take water as an example. Water has a chemical formula H2O. To find the molar mass of water, we add together the molar masses of its parts. Hydrogen (H) has a molar mass of 1.00794 g/mol and oxygen is 15.9994 g/mol. Now, we multiply the value for hydrogen by 2 because there are two hydrogen atoms in every molecule of water, and add the totals together:

1.00794 (2) + 15.9994 = 18.02 g/mol

So water has a molar mass of 18.02 g/mol; one mole of water would weigh 18.02 grams.

In general, the process for finding the molar mass of a compound takes 3 steps:

  1. Determine the molar masses of the individual atomic components.
  2. Multiply those values by their ratio of elements in a single molecule of the compound.
  3. Add the resulting values together.

This process will let you find the molar mass of any compound, no matter how complex. Say we have ethylene, which has a chemical formula of C2H4. What is the molar mass of ethylene? Fist we find the molar masses of carbon and hydrogen, 12.0107 and 1.00794 respectively. Next, we multiply those values by the ratio of elements in a single molecule of the compound and add the resulting values together. One molecule of ethylene has 2 carbon atoms and 4 hydrogen atoms, so:

12.0107(2) + 1.00794(4) = 28.05 g/mol

Ethylene has a molar mass of 28.05 g/mol.

Difference Between Molar Mass And Molecular Mass

It is important to not confuse the concepts of molar mass and molecular mass. Molar mass is a measure of the average weight of a mole of a substance and molecular mass is the weight on an individual molecule of that substance. Molar mass is measured in g/mol and molecular mass is measured in Daltons (Da). The molar mass of a substance is not really an indication of the properties of individual molecules Individual molecules of a substance can differ in weight due to the presence of different isotopes of elements. The molar mass of water might be 18.02 g/mol, but this does not mean that each molecule of water weighs 18.02 Da. Individual water molecules have weights that can range from 18.010 Da to 22.07 Da due to the presence of different isotopes of hydrogen and oxygen.

Importance Of Molar Mass

The concept of molar mass is important in chemistry because it serves as a conceptual bridge between the mass of a substance and the amount of particles in that substance. It is impossible to count individual molecules, so there is no way we could directly measure the amount of particles in a substance (even if we could it would take way too long). We can directly measure the mass of a substance though, so molar mass gives us a way to convert between the mass of a substance and the amount of a substance. The amount of substance is important to know because chemical reactions take place according to strict rules that govern the amounts of reactants and products.

The amount of chemicals required for experimental setups are normally couched in terms of molar mass. Say an experiment calls for 7 moles of carbon dioxide. It is impossible to sit there and literally count out 7 moles of carbon dioxide. Instead, since we know the molar mass of carbon dioxide, we can measure out a comparable mass. Carbon dioxide has a molar mass of 44.01 g/mol, so 7 moles of carbon dioxide corresponds to

44.01 g/mol×7 = 308.07 grams.

So if an experiment calls for 7 moles of carbon dioxide, we know that we need 308.07 grams of carbon dioxide.

Carbon Dioxide As A Compound

Physical Properties

Carbon dioxide is a linear compound made out of two oxygen atoms double bonded to a central carbon atom. Even though C–O bonds are moderately polar (double bonds even more so), carbon dioxide is overall non-polar. The linear geometry of the molecule ensures that any dipole is perfectly canceled out by a corresponding antipode. Despite is non-polarity, carbon dioxide is slightly soluble in water. Carbon dioxide will dissolve in water to form carbonic acid (H2CO3).


Credit: WikiCommons CC0 1.0

Carbon dioxide is one of the main products of combustion, along with water. During combustion, carbon-containing material is burnt and completely oxidized into carbon dioxide and water. The combustion of all carbon-based fuels, (methane, ethane, propane, etc) produce carbon dioxide.

Carbon dioxide can also be used to snuff out a combustion reaction. Since it is denser than air, it will settle to the base of any combustion reaction, displacing the oxygen source. Since carbon dioxide itself can’t be used as a fuel for combustion, the reaction stops.


Carbon dioxide has many natural occurrences. Most obviously, carbon dioxide is the main waste product produced from cellular respiration in aerobic organisms. Oxygen from the atmosphere is used in the redox-reactions that convert organic materials into energy and is converted into carbon dioxide. That carbon dioxide diffuses out of the blood into the lungs and is exhaled. Inability to remove carbon dioxide from the blood effectively can result in damage to the internal organs. Via respiration, the human body produces about 2.3 pounds of carbon per day.

Carbon dioxide is the main source that plants use to fix organic materials. Plants take in carbon dioxide from the atmosphere through microscopic pores in their leaves called stomata. Plants then use energy gathered from sunlight to convert carbon dioxide and water into sugars and molecular oxygen. The oxygen is removed from the plant and becomes the oxygen we breathe.

The exchange of carbon dioxide from the atmosphere into the biosphere and vice versa is called the carbon dioxide cycle. The carbon cycle is vital for life for two main reasons. First, it provides the building blocks for carbohydrates used by living things. Photoautotrophs use energy from sunlight to convert atmospheric carbon dioxide into all the organic molecules that every other living organisms require. Second, carbon dioxide in the atmosphere regulates the temperature of the Earth. Solar radiation entering the Earth’s atmosphere becomes trapped by carbon dioxide and raises the average temperature of the atmosphere. This process is called the “greenhouse effect.” Human emissions of carbon dioxide in the past 150 years have caused a raise in the average temperature of Earth’s climate. Human activity, in particular, the burning of fossil fuels, has raised the concentration of carbon dioxide in the Earth’s atmosphere to over 43% more than pre-industrial times. The result has been an average temperature increase of over 1 °F in the past 100 years of human industrial activity.

In the food industry, carbon dioxide is used as an additive to food and drinks to give it a fizzy behavior and slightly acidic taste.  Carbonic acid and the released carbon dioxide is what gives soda and other carbonated beverages their effervescence and crisp taste.

In oil extracting, carbon dioxide gets injected into crude oil deposits to change its viscosity and allow it to flow better from the natural deposit into a reservoir. Solid carbon dioxide (dry ice) is used as an industrial cooling agent, and its spontaneous sublimation in air is used to provide fog-visual effects.


About The Author

Alex is a graduate of UMSL with his MA, with an area of concentration in the history and philosophy of science. When he isn't nerdily stalking the internet for science news, he enjoys tabletop RPGs and making really obscure TV references.