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Balancing Chemical Equations



Law of Conservation of Mass- Mass is not created nor destroyed just transferred

                                     A balanced equation demonstrates that reactants are completely converted to products.

Reactants-the compounds that exist before a reaction has occurred.

Products-The compounds that exist after the reaction has occurred.

Coefficients-The number in front of a compound, element or ion. Determines the number of moles of that species.

Note-Chemist do not write 1's, we just write the formula. It does count as a 1, but it is not there.

Reading a chemical reaction.

2H2(g) + O2(g) 2H2O(l)

2 moles of hydrogen gas reacts with 1 mole of oxygen gas to form 2 moles of liquid water.

+means reacts with             means to form

Here are some balancing videos to help you through this.

Balancing these Decomposition Reactions

___Ag2S ___Ag+___S 



___Fe2O3 ___Fe +___O2 

 ___KClO3 ___KCl +___O2 



Balancing these Synthesis Reactions

___Mg+ ___ O2 ___ MgO

 ___ S8+___ O2___ SO2

 ___ P+___ Cl2___ PCl3

___N2 +___ O2  ___N2O5

 ___N2  + ___H2    ___NH3

 ___Al + ___O2 ___Al2O3


Balancing these Single Replacement Reactions

___Cl2 + ___NaBr ___NaCl + ___Br2

 ___Mg + ___HCl ___MgCl2 + ___H2

___Cu + ___AgNO3 ___Ag + ___Cu(NO3)2

___Al + ___Fe2O3 ___Al2O3 + ___Fe

 ___Na  + ___H2O ___NaOH + ___H2


Balancing these Double Replacement Reactions

___ CaCO3 + ___ HCl ___ CaCl2+ ___ H2CO3

___ NaCl + ___ H2SO4 ___ Na2SO4+ ___ HCl

 ___ Al(NO3)3 + ___ H2SO4 ___ Al2(SO4)3+ ___ HNO3

___ MgCl2+____ Na3PO4 ___ Mg3(PO4)2+ ___ NaCl


Balancing these Acid Base Neutralization Reactions

___ HCl  + ___ Ca(OH)2 ___ CaCl2 + ___ H2O

___ HC2H3O2 +  ___ Al(OH)3 ___ Al(C2H3O2)3 +___  H2O

 ___ HNO3 +  ___ Ba(OH)2 ___ H2O +  ___ Ba(NO3)2


Past Regents Balancing Questions- Follow link for answers

Aug 2010-7 A balanced equation representing a chemical reaction can be written using
(1) chemical formulas and mass numbers
(2) chemical formulas and coefficients
(3) first ionization energies and mass numbers
(4) first ionization energies and coefficients

June 2006-7 Given the balanced equation representing a reaction:
F2(g) + H2(g) ==> 2HF(g)
What is the mole ratio of H2(g) to HF(g) in this reaction?
(1) 1:1      (3) 2:1
(2) 1:2      (4) 2:3


Chemical Demonstration Videos