10 April 2010

Balancing chemical equations

Here are the steps to balancing a chemical equation.
Here's a brief summary:
(1) Law of Conservation of MassFor each element, the number of atoms on the left and the right of the equation are the same (e.g., 3H2 on the left and 2H on the right is NOT Ok).
(2) To balance the equation, you can ONLY change the coefficients, NOT the subscripts (e.g., changing CO2 to 3CO2 is OK. Changing CO2 to CO4 is not.)
(3) To calculate the number of atoms for each atom, you MULTIPLY the coefficient times the subscripts (e.g., 3 CO2 = 3 Carbons and 6 Oxygens)
(4) You MUST have only integer coefficients when you are finished (e.g., 6.5 O2 is not ok, 13 O2 is ok)
(5) You MUST have the lowest possible integer coefficients when you are finished 

For the textbook description, READ our textbook:

For a movie showing each of these steps, see the following website:



STEP 3: Balance the Hydrogens

STEP 4: Balance the Oxygens

FINAL STEP: Make sure all coefficients are integers!
For those of you who want to CHECK your answers, please see the following web site: www.webqc.org/balance.php
NOTE: There are many example equations that you can PASTE into this website and test how to balance them. For example:

  • Fe + Cl2 = FeCl3
  • KMnO4 + HCl = KCl + MnCl2 + H2O + Cl2
  • K4Fe(CN)6 + H2SO4 + H2O = K2SO4 + FeSO4 + (NH4)2SO4 + CO
  • C6H5COOH + O2 = CO2 + H2O
  • K4Fe(CN)6 + KMnO4 + H2SO4 = KHSO4 + Fe2(SO4)3 + MnSO4 + HNO3 + CO2 + H2O

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