Balancing Chemical Equations :)
Atoms are neither created nor destroyed in a chemical reaction. When we write a chemical equation we must, therefore, ensure we have the same number of atoms of each element on each sideof the chamical reaction. We do this bny balancing the equation as follows:
1 - Write down the formulae of all the reactants and all the products. It may help you to write these in words.
2 - Now inspect the equation and count the number of each element on each side. As the atoms of each element cannot be created nor lost in the chemical reaction, we must balance the number of each element on each side.
3 - Decide which numbers must be placed in front of each formula to ensure that the same number of each atom is present on each side of the equation.
It is most important that the formulae of the reactants and products in not altered; only the total number of each may be changed.
Worked example:
Step 1 - Wen iron(III) oxide is reduced to metallic iron by carbon monoxide, the carbon monoxide is oxidised to carbon dioxide. The (III) in iron(III) oxide indicates that the iron has an oxidation state of +3.
Iron(III) oxide + carbon monoxide ------> iron + carbon dioxide
The formulae are:
Fe2O3 + CO -------> Fe + CO2
Step 2 - On inspection we note that there are two iron atoms in the oxide on the left-hand side but only one on the right-hand side. In order to belance the number of iron atoms we write:
Fe2O3 + CO -------> 2Fe + CO2
Step 3 - Next we count the oxygen atoms: three in the oxide plus one in the monoxide, on the left-hand side. As there are only two on the right-hand side in carbon dioxide, we must double the number of CO2 molecules in order to balance the number of oxygen atoms:
Fe2O3 + CO -------> 2Fe + 2CO2
Step 4 - On checking we see we have solved one problem but created a new one. There are now two carbon atoms on the right but only one on the left. Doubling the number of CO molecules balances the carbon atoms but unbalances the oxygen atoms again! If we examine the equation again, we see that in the reaction between Fe2O3 and CO, each CO molecule requires only one oxygen atom to form CO2. Thus three CO molecules combine with the three oxygen atoms lost from Fe2O3. Three CO2 molecules will be formed:
Fe2O3 + 3CO -------> 2Fe + 3CO2
Step 5 - Conclusion: the equation is now balanced.
If you follow these steps everytime you are trying to balance any equation you will never go wrong :)
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