Balancing Chemical Reactions

Step 1 Count the atoms on the left side and on the right side of a reaction. Mg + O2  MgO left side right side

Step 2 Make the number of atoms on each side of the equation the same by only changing the number in front of the compound (coefficient). Never change the compound itself by changing the little numbers in the compound (subscript numbers).

Step 3 Always double check that the number of atoms on the right side of the equation are equal to the left side of the equation. Example: Balance the following equation: __Mg + __O2  __MgO 2Mg + 1O2  2MgO

Tips on Balancing Equations 1) Try to balance atoms with the greatest atomic number first Example: __FeCl3 + __CuS  _1_Fe2S3 + __CuCl2 2FeCl3 + 3CuS + 1Fe2S3 + 3CuCl2

Tips on Balancing Equations Balance the elements that are by themselves last (usually oxygen and hydrogen) Example: 1C3H8 + __O2  CO2 + H2O 1C3H8 + 5O2  3CO2 + 4H2O

Tips on Balancing Equations Balance polyatomic ions as if they are one element if possible Example: __Mg(NO3)2 + __K3PO4  __Mg3(PO4)2 + __KNO3 3Mg(NO3)2 + 2K3PO4  1Mg3(PO4)2 + 6KNO3