A chemical equation is a mathematical representation of a chemical reaction. A well balanced chemical equation is exact. It has the actual numbers of the molecules or atoms that are involved in the reaction.
Chemical equations are similar to recipes. If one mixes these two ingredients there will be a chemical reaction of this new substance. With chemistry they are called formulas instead of recipes and it is important to have them balanced.
When there is a chemical reaction, the reactions is converted to products. The number of atoms remains the same before and after the reaction. This is referred to as the law of conversion mass. The sides must balance as mass is neither lost or created. The amount of matter in the universe is constant.
Chemical equations are written in a left to right sequence. The reactions are written on the left hand side and the products are written on the right hand side. 2H2 + 02→2H20 In this equation four molecules of hydrogen are combining with 2 molecules of oxygen to give two molecules of water.
Let’s take a look at some tips that can help us balance equations.
1. You may only put numbers in front of the molecules. You can never alter the subscript, as it would alter the formula. So the coefficient can be changed, but not the subscript.
2. Begin by counting and making note of the elements present on each side of the equation.
3. Count the number of molecules of each element on both sides of the equation.
4. Look for atoms that make up a group or family, like sulphate, phosphate or ammonium. These will go throughout the chemical reaction the same. Treat them as an indivisible team. They should be balanced as a whole unit.
With these things in mind we can go back to our original example. 2H2 + 02→2H20
In this reactions one molecule of hydrogen and an atomic form of oxygen are enough to make a molecule of water. H2 + O2 → H2O . This would be unbalanced. So the equation is balanced to
2H2 + 02→2H20 .
Here are some more examples of equations before and after balancing.
Fe + Cl2 → FeCl3 (unbalanced)
2Fe + 3Cl2 → 2FeCl3
KMn04 + HCl → KCl + MnCl2 + H20 + Cl2 (unbalanced)
2KMn04 + 16HCl → 2KCl + 2MnCl2 + 8H20 + 5Cl2
Here are some other examples to help practice balancing equations
.
_____ Sn02 + _____H2 → _____Sn + _____ H20
_____ BF3 + _____Li2S03 → _____B2(S03)3 +_____LiF
_____SeCl6 +______ 02 → ______Se02 + ______ Cl2
With a little practice balancing chemistry equations become quite natural. It is suprizing how quickly one can can catch on.
Sources:
http://richardbowles.tripod.com/chemistry/balance.htm#part3b
