Chemical Formulas and Equations

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Chemical Equations
A chemical equation represents what takes place in . An example of a chemical equation would be:
2Na + Cl2 → 2NaCl
The formulas on the left side of the equation are the . These are the substances used to start a chemical reaction. The , →, means either "yields" or "reacts to form." The formulas to the right of the arrow are the . These substances are formed during the chemical reaction. The numbers in the chemical formulas are important. The is the big number in front of the chemical formulas that tells the number of atoms, molecules, or formula units involved in the reaction. The coefficient in front of the Na is 2, which means there are 2 sodium present in the reactants. If the coefficients is 1, this is usually understood, so the coefficient 1 is not written.
Sometimes it helps to indicate the states or phases of the substances in a chemical reaction. We can do this by placing certain labels, which stand for the various phases, following the formula of a substance in a chemical equation. Here are some labels used in chemical equations.:
(g)=gases (l)=liquid (s)=solid (aq)=aqueous solution
When we use the labels, this equation becomes:

2Na(s) + Cl2(g) → 2NaCl(s)
If we were to simply put the formulas of the chemicals on the left and right without saying how much of it was going to react, then we would run the risk of saying that the mass of what we end up with is different than the mass of what we started with. This would not follow the Law of Conservation of .You need to balance the equations by sticking numbers in front of the chemicals on the left and right sides of the equation until there are the same number and kinds of atoms present on each side of the .