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Laws of Chemical Combination


The balancing of chemical equations is based upon Dalton’s atomic theory and law of conservation of mass. According to Dalton’s atomic theory atom is the smallest unit of an element that takes part in chemical reactions and that during chemical reactions atoms are neither created nor destroyed. Therefore, the number of atoms of each element should remain same before and after the reaction.

To make the number of atoms of all the elements equal on both the sides in a skeletal equation is known as balancing. During balancing, the symbols and formulae of various species given in the equation are multiplied with appropriate coefficients. A coefficient is a small whole number, like the coefficients used in algebraic equations. The simple equations can be balanced by Hit and trial method. The following steps may be followed while balancing the chemical equations by this method:

Step 1. Write the correct skeleton equation. The skeleton equation contains the formulae of only one molecule of each reactant and product. Once you are satisfied that the skeleton equation is correct, do not change the subscripts in any of the formulae.

Step 2. Start with the compound that has the maximum atoms or the maximum kinds of atoms and the atoms present in it are balanced first.

Step 3. Balance elements that appear only once on each side of the arrow first. Then balance elements that appear more than once on a side.

Step 4. Elementary substances are balanced last of all.

Step 5. If required the whole equation is multiplied by some suitable number in order to make all the coefficients whole numbers.

The application of these rules is illustrated in the following solved examples.