Rules for Balancing Chemical Equations

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					                                                                      SNC2D – Chemistry: Chemical Reactions



                           Rules for Balancing Chemical Equations
1. Write the correct skeletal equation. Remember the elements H, O, F, Br, I, N, Cl which exist on their own as
   diatomic molecules (e.g. H2, O2, F2, etc.)
2. You cannot change a molecular formula (you cannot add, remove, or change a subscript)
3. Change coefficients as needed so that for each atom type, the number of atoms is the same on both sides of the
   equation.
            (a) List all the atom types on both sides of the equation (i.e. list the atom types on the reactants and
                the products sides)
             (b) Change coefficients one at a time to balance the number of atoms of each type. Every time you
                 change a coefficient, recount the atoms on that side of the equation.
             (c) As a very general rule of thumb, balance H and O last.
4. Reduce your answer to lowest terms. Do not use fractions.

Examples:

    1. ____ CH4 + __2__ O2 → ____ CO2 + __2__ H2O                          Reactants                Products
                                                                          C         1           C              1
                                                                          H         4           H              4
                                                                          O         4           O              4


    2. ____ FeCl3 + ____ Na2S → ____ Fe2S3 + ____ NaCl                     Reactants                Products




    3. ____ NO + ____ H2 → ____ N2 + ____ H2O
                                                                           Reactants                Products




    4. ____ KClO3 → ____KCl + ____ O2
                                                                           Reactants                Products




    5. ____ Fe2O3 + ____ P → ____ Fe + ____ P2O5                           Reactants                Products
                                                         SNC2D – Chemistry: Chemical Reactions



                    Balancing Chemical Equations - Practice

1. ____ C4H10 + ____ O2 → ____ CO2 + ____ H2O




2. ____ Ca3(PO4)2 + ____ SiO2 + _____ C → ____ P4 + ____ CaSiO3 + ____ CO




3. ____ H2O + ____ SO3 → ____ H2SO4




4. ____ (NH4)2Cr2O7 → ____N2 + ____ Cr2O3 + ____ H2O




5. ____ Bi2O3 + ____ H2 → ____ Bi + ____ H2O




6. ____ FeCl3 + ____ (NH4)2S → ____ Fe2S3 + ____ NH4Cl




7. ____ C10H16 + ____ O2 → ____ CO2 + ____ H2O
                                                         SNC2D – Chemistry: Chemical Reactions


8. ____ NaI + ____ MnO2 + _____ H2SO4 → ____ Na2SO4 + ____ MnSO4 + ____ H2O + ____ I2




9. ____ Mg(OH)2 + ____ HNO3 → ____ Mg(NO3)2 + ____ H2O




10. ____ FeCl3 + ____ NaOH → ____ Fe(OH)3 + ____ NaCl




11. ____ H2SO4 + ____ Mg → ____ MgSO4 + ____ H2




12. ____ NaClO3 → ____ NaCl + ____ O2




13. ____ AsCl3 + ____ H2S → ____ As2S3 + ____ HCl




14. ____ Pb(NO3)2 → ____ PbO + ____ NO2 + ____ O2




15. ____ NaOH + ____ H3PO4 → ____ Na3PO4 + ____ H2O

				
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