SO2 + O2 = SO3

Balanced Chemical Equation – Solution

2SO2 + O2 → 2SO3

The coefficients show the number of particles (atoms or molecules), and the indices show the number of atoms that make up the molecule. New substances are formed as a result of the rearrangement of the original atoms. As a result of a chemical reaction, atoms of chemical elements do not disappear anywhere and new ones do not appear, their number remains unchanged – this follows from the law of conservation of mass of substances.

Chemical Reaction Information

Sulfur Dioxide + Dioxygen = Sulfur Trioxide

This is an oxidation-reduction (redox) reaction. SO2 is a reducing agent, O2 is an oxidizing agent.

  • 2 SIV  4 e  2 SVI (oxidation)
  • 2 O0 + 4 e  2 O-II (reduction)

Reaction Type


Substances that react are called starting materials or reactants. The substances that form as a result are called reaction products.


SO2 – Sulfur dioxide

  • Other names: Sulfurous anhydride.
  • Appearance: Colorless gas.


  • Names: Dioxygen, Oxygen.
  • Appearance: Odourless compressed gas.


SO3 – Sulfur trioxide

  • Other names: Sulfuric anhydride.
  • Appearance: Colorless to white crystalline solid which will fume in air.
Similar Examples of Equalizing a Chemical Reaction
O2 + SO2 + CaCO3 → CO2 + CaSO4
H2O + O2 + SO2 → H2SO6
H2O + O2 + SO2 → H2SO4
H2O + O2 + SO2 → H2SO8
O2 + SO2 → SO34
O2 + SO2 → SO3
H2O + O2 + SO2 + NaCl → HCl + Na2SO4
O2 + SO2 → SO5
O2 + SO2 + CaO → CaSO4
O2 + SO2 + Fe → Fe2(SO4)3

Alexander Stephenson

Candidate of Chemical Sciences, editor-in-chief of Lecturer at several international online schools, member of the jury of chemistry competitions and author of scientific articles.

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