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# Back to Math of Chemistry Links

 Balancing Chemical Equations

Definitions

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.

2H2(g) + O2(g) è2H2O(l)

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

+means reacts with             èmeans to form

Balancing these Decomposition Reactions

 ___Ag2S è ___Ag+___S  __H2CO3è___H2O+___CO2  ___NH3è___N2+___H2 ___Fe2O3 è___Fe +___O2   ___KClO3 è___KCl +___O2  __Ca(OH)2è___CaO+___H2O

Balancing these Synthesis Reactions

 ___Mg+ ___ O2 è___ MgO  ___ S8+___ O2è___ SO2  ___ P+___ Cl2è___ PCl3 ___N2 +___ O2  è___N2O5  ___N2  + ___H2    è___NH3  ___Al + ___O2 è___Al2O3

Balancing these Single Replacement Reactions

 ___Cl2 + ___NaBrè ___NaCl + ___Br2  ___Mg + ___HCl è ___MgCl2 + ___H2 ___Cu + ___AgNO3è ___Ag + ___Cu(NO3)2 ___Al + ___Fe2O3è ___Al2O3 + ___Fe  ___Na  + ___H2O è ___NaOH + ___H2

Balancing these Double Replacement Reactions

 ___ CaCO3 + ___ HCl è ___ CaCl2+ ___ H2CO3 ___ NaCl + ___ H2SO4 è ___ Na2SO4+ ___ HCl  ___ Al(NO3)3 + ___ H2SO4 è ___ Al2(SO4)3+ ___ HNO3 ___ MgCl2+____ Na3PO4 è___ Mg3(PO4)2+ ___ NaCl

Balancing these Acid Base Neutralization Reactions

 ___ HCl  + ___ Ca(OH)2 è ___ CaCl2 + ___ H2O ___ HC2H3O2 +  ___ Al(OH)3 è ___ Al(C2H3O2)3 +___  H2O  ___ HNO3 +  ___ Ba(OH)2 è ___ H2O +  ___ Ba(NO3)2

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

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