Chemical equations and balancing chemical equations

Atoms can be neither created nor destroyed in an ordinary chemical reaction, so there must be the same number of atoms on both sides of the equation.

These numbers are found in a chemical equation: ·

 

Subscripts

 

The small numbers to the lower right of chemical symbols. Subscripts represent the number of atoms of each element in the molecule. ·

 

Coefficients

 

The large numbers in front of chemical formulas. Coefficients represent the number of molecules of the substance in the reaction.

 

This is an example of a chemically balaned equation

 

Consider the example of:

 

(NH4)2CO3 ---> NH3 + CO2 + H2O

 

The first thing to do is choose a starting point. If we choose the carbon as the starting point, we go nowhere, since there is already one carbon on each side. Choosing oxygen is not good, because the oxygen is divided between two species on the right side. The interesting part is in the ammonium (NH4) ion. If we start with the nitrogen on the left (in the ammonium ion), we see that there are two nitrogens and therefore we must put at "2" in front of the ammonia on the right side.

 

(NH4)2CO3 ---> 2 NH3 + CO2 + H2O

 

Since we are already working with the ammonia, now consider the hydrogens that make up the rest of the molecule: the six hydrogens in the ammonia plus the two hydrogens in the water make eight hydrogens. Bouncing back across to the left side, we count eight hydrogens; since no other atomic species have been changed, we can count up everything and see that the reaction is now balanced:

 

2 N, 8 H, 1 C, and 3 O on each side.

 

Notice how the reaction itself led us through the steps of the balancing process. A more complex reaction would have involved more steps, but the process would have been the same. Knowing how to do this is important because if you know how to balance an equation, you will never have an unbalanced equations again.

 

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Stoichiometric Equations