What are the products of the following combustion reaction?
2c2h2(g) + 5o2(g) →

4CO2 + 2H2O

Explanation:

A complete combustion reaction produce carbon dioxide, water and energy. That is:

Fuel + O2 → CO2 + H2O + Energy

In the reaction given, it will be:

2C2H2 + 5O2 → X CO2 + Y H2O + Energy

Where X and Y are de moles of CO2 y H2O produced,  respectively. What is needed now is to balance the equation and find out the value of X and Y.

You can see that from de left side of the equation you have 4 H (2 C2H2) so Y most be equal to 2 so you have 4 H at de right side of the equation (2 H2O). On the other hand, you have 4 C at the left side of the equation (2 C2H2) and just 1 C at the right side ( CO2), in consequence X  most be equal to 4 so you have 4 C at both sides (4 CO2). The final equation would be:

2C2H2 + 5O2 → 4CO2 + 2H2O + Energy

To confirm this, you can notice than you have the same amounts of moles of oxygen at both sides: 10 al the left side (5O2) and 10 at the right side (4CO2 + 2H2O, i.e 8 + 2 = 10)

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