Question

Methane undergoes complete combustion. a) substitute symbols and formulas for words b) predict the products. If no reaction occurs, write "NR" after the yields sign. c) include abbreviations for the physical state d) balance the equation

Answer 1

a) assuming we are meant to write the formulas for the compounds in the question, we want to write the formula for methane. Methane is compouded by 1 carbon atom and 4 hydrogen atoms, so it has the formula: CH₄.

b) we know it is a complete combustion. A complete combustion of some compound is always its reaction with oxygen (O₂) to form only water (H₂O) and carbon dioxide (CO₂).

So, the incomplete and unbalanced equation is:

$CH_4+O_2\to CO_2+H_2O$

c) The combustion occurs in high temperature and in gaseous form. Thus, all compounds are in gaseous form (g).

The unbalcend equation is then:

$CH_4\, (g)+O_2\, (g)\to CO_2\, (g)+H_2O\, (g)$

d) To balance the equation, we can leave CH₄ unchanged and balance the others base on it.

The carbon, C, only appears in CH₄ and CO₂, and in both we have only 1, so it is balanced.

The hydrogen, H, appears in CH₄ and H₂O. We have 4 on the left side and 2 on the right side, so we can double H₂O to fix it:

$CH_4\, (g)+O_2\, (g)\to CO_2\, (g)+2H_2O\, (g)$

Now, we have 2 oxygen, O, on the left side and 4 on the right side, so we also need to double O₂ to get it right.

So, the balanced equation is:

$CH_4\, (g)+2O_2\, (g)\to CO_2\, (g)+2H_2O\, (g)$