Toluene (methylbenzene) and Oxygen Reaction (Combustion) | C6H5CH3 + O2

Toluene, 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 is achieved. Otherwise, carbon monoxide can be given as another product if the supplied oxygen gas amount is not sufficient for the toluene combustion.

C6H5CH3 + O2 → CO2 + H2O





In this tutorial, we will discuss followings.

Balanced reaction of combustion of toluene and oxygen Change of oxidation numbers of elements in toluene combustion Thermal energy of the reaction Health, safety and environmental impacts due to the combustion of toluene


Toluene chemical properties important in the combustion procedure

Toluene is an organic compound which contains seven carbon atoms and eight hydrogen atoms.

  • Toluene is a clear colorless liquid .
  • Flash point of benzene: 4.40C
  • Boiling point: 110.60C


Stoichiometric balanced chemical reaction of toluene and oxygen gases

toluene combustion with oxygen gas - C6H5CH3 + O2

According to the balanced chemical equation, two moles of toluene react with eighteen moles of oxygen gas and produce fourteen moles of carbon dioxide and eight moles of water.

2C7H8(l) + 18O2(g) → 14CO2(g) + 8H2O(g)



Change of oxidation numbers in toluene combustion

Because, combustion process is a process a redox reaction (oxidation - reduction), oxidation numbers of carbon and oxygen atoms are are changed during the reaction as below.

  • In toluene molecule, there are total of seven carbon atoms.
  • The carbon atom which is not in the benzene ring is at -3 oxidation state.
  • The carbon atom which has not made bonds with hydrogen atoms is at 0 oxidation state. All other five carbon atoms are at -1 oxidation state.
  • However, all of those carbon atoms are oxidized to carbon dioxide molecules. In carbon dioxide molecule, carbon is at +4 oxidation state.
  • Oxygen is at 0 oxidation state in oxygen molecule (O2) and that those oxygen atoms are reduced to -2 oxidation state.


Thermal energy and heat generation

Standard enthalpy of combustion of toluene (ΔHc0(C6H5CH3,(l))) = -3910.3 kJ mol-1



Health and safety of toluene

  • Both toluene liquid and vapour is highly flammable.
  • Causes skin irritation.
  • Can be fatal, if inhaled or swallowed


Questions



Who generates more energy in combustion, benzene or toluene?

Toluene generates more energy than benzene.



If 1kg of toluene is burnt, how much energy will be released?

  • Calculate how much amount (mol) of toluene contains in 1kg of toluene.
  • Amount of toluene = 1000 g / toluene molar mass
  • Amount of toluene = 1000 g / 92.14 g mol-1
  • Amount of toluene = 10.85 mol

  • Released heat = number of moles * standard heat of combustion
  • Released heat = 10.85 mol * 3910.3 kJ mol-1
  • Released heat from toluene combustion = 42,438.68 kJ






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