Propane and Oxygen Reaction (Combustion) | C3H8 + O2

Propane, an alkane compound in organic chemistry, readily burns with oxygen gas and heat is released as a result of combustion. As chemical products, carbon dioxide and water are given if complete combustion of propane is achieved. Otherwise, some amount of carbon monoxide gas can be given as another product if the supplied oxygen gas amount is not sufficient for a complete combustion process.

C3H8 + O2 → CO2 + H2O





In this tutorial, we will discuss followings.

Balanced reaction of propane and oxygen Oxidation number change of elements in propane combustion Thermal energy of the reaction Health, safety and environmental impacts due to combustion of propane


Propane

Propane is included one chemical in LPG tanks which are used for domestic and industrial combustion purposes.

Propane contains three carbon atoms and eight hydrogen atoms. Because propane's flash point is a -1040C, propane is a highly flammable organic compound.



Stoichiometric balanced chemical reaction of propane and oxygen gases


balanced equation of propane combustion with oxygen gas - C3H8 + O2

One moles of propane react with five moles of oxygen gas and produce three moles of carbon dioxide and four moles of water.

C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g)



Change of oxidation numbers in propane combustion

Because, above mentioned combustion process is a redox reaction, oxidation numbers of carbon and oxygen atoms are changed as mentioned below.

  • In propane molecule, there are three carbon atoms exist and they are in different oxidation states (-3 and -2) as following figure. However, all carbon atoms are oxidized to carbon dioxide molecules. In a carbon dioxide molecule, carbon is at +4 oxidation state. So, carbon atom is oxidized during the reaction.
  • Oxygen is at 0 oxidation state in oxygen molecule (O2) and that those oxygen atoms are reduced to -2 oxidation state. Therefore, oxygen in oxygen molecule is reduced during the combustion process.
oxidation numbers of carbon atoms in propane C3H8



Thermal energy and heat generation

We can have two different combustion energies as higher heating value and lower heating value.


Higher heating value of propane combustion

Standard enthalpy of combustion of propane (ΔHc0(C3H8,(g)) = -2219.9 kJ mol-1

This means that, if 1 mol of propane is burnt and products are reached to the standard status, 2219.9 kJ of energy is released to the outside environment.



Lower heating value of propane combustion

Standard enthalpy of combustion of propane (ΔHc0(C3H8,(g)) = -2043.455 kJ mol-1

This means that, if 1kg of propane is burnt and products are not reached to the standard status, 2043.455 kJ of energy is released.



Health and safety

Hazards are identified as GHS classifications.

  • H220: Propane is an extremely flammable gas.

Due to extremely flammable property of propane, should be careful when LPG is used because propane is a main component in LPG.





Example Calculations related to combustion of propane


If 100g of propane is burnt with excess oxygen gas, calculate how much energy should be generated. Consider, products are reached to the standard state.

Before doing a such calculation, it is good to summarize the steps of calculation.

  1. Calculate molar mass of propane
  2. Calculate amount (mol) of combusted oxygen gas
  3. Calculate generated heat due to the combustion

Calculate molar mass of propane

  • Molar mass of propane = (12*3) + (1*8)
  • Molar mass of propane = 44 g mol-1

Calculate amount (mol) of combusted propane gas

Use n = m/M equation.

  • Amount (mol) of combusted propane gas = (1 * 103 g) / 44 g mol-1
  • Amount (mol) of combusted propane gas = 22.73 mol

Calculate generated heat due to the combustion of propane

  • Generated heat due to the combustion = Combusted amount (moles) of propane * Standard enthalpy of combustion of propane
  • Generated heat due to the combustion = 22.73 mol * -2219.9 kJ mol-1
  • Generated heat due to the combustion = 50,452.27 kJ


Questions



Propane is included as a combustible material in the Liquified Petroleum Products (LPG) gas cylinder. Why Propane is liquified as like that?

Considering physical properties of alkane compounds, Propane is a gas at room temperature. But in LPG tanks, both propane and butane gases are stored as liquids by pressurizing of the gases. Reason for this liquidization process is storing more combustible fuel compared to the gases state fuels.



Is burning propane for energy generation is more environmental friendly than diesel burning?

Yes. Considering environmental pollution, diesel generates more quantities of carbon dioxide (CO2) and sulfur dioxide (SO2) compared to propane.



Is oxidation number of carbon atom changed during the complete combustion of propane?

Because combustion process is always an oxidation - reduction reaction, oxidation number of one or more atoms should be changed during the reaction. In propan molecule,e carbon atoms are oxidized to higher oxidation stated while oxygen atoms in oxygen molecules are reduced.



Does Propane react with oxygen?

If a spark is available, reaction of Propane and oxygen gases can be an explosive one.







Lewis structure of propane molecule Toluene (methylbenzene) combustion with oxygen gas Benzene combustion with oxygen gas methanol combustion with oxygen gas Ethanol combustion with oxygen gas Ethane and oxygen reaction Methane and oxygen reaction Nitrogen trichloride and water reaction What is the limiting reagent and how to decide limiting reagent in reactions Sandmeyer reactions of benzenediazonium chloride Reactions of hydrogen sulfide Calcium bromide and sodium carbonate reaction Alkene and hydrogen reaction Ethane and oxygen gas reaction Methane and oxygen gas reaction









Related tutorials to propane

1,3-diphenylpropane 1-propanol to 2-bromopropane 1-propanol to 2-bromopropane conversion 2-propanol to 1-propanol Ethanol to propanol Propanol to propanone