Question

What are the products of the following combustion reaction? 2C2H2(g) + 5O2(g) →

Answer 1

Answer: 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)

Answer 2

A combustion reaction of an  will generally produce CO2 and H20 -- carbon dioxide and water and/or an oxide

looking at the combustion material C2H2, you know that the end products will be CO2 and H20, so the question is how much of each will you get

well, look at the total amount of carbon atoms, 2 C2, which means a total of 4 carbon atoms in this reaction, since only CO2 has carbon atoms, that means there must be 4 CO2 as an end product and 4 CO2 will use up 4 of 5 O2 molecule leaving only 1 O2 molecule for the H2 reaction.

now O2 has a total of 2 oxygen molecules whereas H20 has only a single oxygen molecule, hence the end product must have 2 H20

check that the H atoms balance out on both sides