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Balancing chemical equations:rules and guidelines in balancing chemical equations

Answer Text:
Balancing chemical equations.
- A chemical equation is only valid if it is balanced.
- A chemical equation is said to be balanced if the number of each atom on the reactants side is equal to that on the products side.
- This is because atoms are neither created nor destroyed during a chemical reaction.
Rules and guidelines in balancing chemical equations.
Step 1: Write the chemical equation in words.
Example: Copper metal + oxygen gas.
Step II: Write the correct formulae of both reactants and products
Example: #Cu + O_2 → CuO#
Step III: Check whether the number of atoms of each element on the reactants side is equal to that on the products side.
- If equal proceed to step (V);
- If not equal proceed to step (IV).
Example: #Cu + O_2 → CuO#
- In this case there are two oxygen atoms on the reactants side yet there is only one oxygen atom on the products side. Thus we proceed to step IV
Step IV: Multiply the chemical formula containing the unbalanced atoms with the lowest common multiple.
Example:# Cu + O_2 → CuO#
- In this case the chemical formula with the unbalanced atom is CuO on the products side. We thus multiply it by 2.
- The new equation now reads: #Cu + O_2 → 2CuO#
Step V: check again to ensure that all atoms are balanced.
- If all atoms are balanced proceed to step VI.
- If not then repeat step IV until all atoms are balanced.
Example: #Cu + O_2 → 2CuO#
- In this case multiplying CuO by 2 offsets the balancing of Cu; which is now unbalanced!
- We therefore repeat step IV in order to balance Cu.
- There is only 1 Cu atom on the reactants side yet there are 2 Cu atoms on the products side.
- We thus multiply the formula with the unbalanced atom (s) by the lowest common multiple, in this case 2.
- The new equation at this step thus becomes: #2Cu + O_2 →2CuO# - We then repeat step V; in this case all atoms are now balanced.
Step VI: The physical states of the reactants and the products are then indicated.
- If this is not done the chemical equation is considered incorrect.