Butane, C4H10 is burned completely in excess oxygen, write the balanced chemical formula for the reaction, name the products and type of reaction.

We need to think about the number of atoms of each element in the reactants and ensure these are the same in the products.

This is the basic UNBALANCED equation.

C₄H₁₀ + O₂ ----> CO₂ + H₂O

So we have 4 C atoms on the left so will need 4 CO₂ molecules on the right:

C₄H₁₀ + O₂ ----> 4CO₂ + H₂O

Similarly we have 10 H atoms on the left so therefore need 5 H₂O molecules on the right (as each H₂O molecule has 2 H atoms)

C₄H₁₀ + O₂ ----> 4CO₂ + 5H₂O

Now we just need to balance the O atoms. We have 8 + 5 on the right hand side = 13, as oxygen is present as O₂ (ie two O atoms in each molecule) we therefore need 7.5 O₂ molecules on the left hand side:

C₄H₁₀ + 7.5O₂ ----> 4CO₂ + 5H₂O

or to keep in whole numbers,multiply everything by two:

2C₄H₁₀ + 13O₂ ----> 8CO₂ + 10H₂O

The name of the products are CO₂ = carbon dioxide and H₂O = water. The type of reaction is a combustion reaction.