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Balancing Equations
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CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)
Chemical Equations Chemical Equations are concise representations of chemical reactions. CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)
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Anatomy of a Chemical Equation
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g) Reactants appear on the left side of the equation.
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Anatomy of a Chemical Equation
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g) Products appear on the right side of the equation.
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Anatomy of a Chemical Equation
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g) The states of the reactants and products are written in parentheses to the right of each compound.
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Anatomy of a Chemical Equation
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g) Coefficients are the numbers which appear before a compound
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Anatomy of a Chemical Equation
CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g) Subscripts are the numbers which appear in a compound
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Subscripts and Coefficients
Subscripts tell the number of atoms of each element in a molecule Coefficients tell the number of molecules CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g) The coefficient 2 tells us that we have two total water molecules. Coefficients tell the number of molecules. The subscript 2 informs us that this compound consists of two hydrogen atoms bonded to one oxygen atom. Subscripts tell us the number of atoms in a compound.
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Subscripts and Coefficients
To know how many total atoms there are of a specific element we multiply the subscript by the coefficient. For example: Multiply the subscript 2 by the coefficient 2 to get a total of 4 hydrogen atoms. CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g) To know how many oxygen atoms we have on the product side we would have to add the oxygen in carbon dioxide to the oxygen in water: 2 O + 1 O = 3 O
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Balancing Equations
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Balancing Equations Law of Conservation of Matter:
In a chemical reaction, matter can be neither created nor destroyed.
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Balancing Equations In other words:
The number of atoms of each type of element must be the same on each side of the equation.
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Balancing Equations H2 + O2 H2O
The subscripts on Hydrogen and Oxygen cannot be changed. The subscripts on water cannot be changed. NEVER CHANGE SUBSCRIPTS!
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Balancing Equations H2 + O2 H2O
If the subscripts cannot be altered, how can the atoms be made equal? Adjust the number of atoms by changing the coefficients.
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Practice H2 + O2 H2O Count the atoms on each side. Reactant side:
2 atoms H 2 atoms O —Product side: 2 atoms H 1 atom O
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Practice H2 + O2 2H2O Count the atoms on each side. Reactant side:
2 atoms H 2 atoms O —Product side: 4 atoms H 2 atoms O Hydrogen is no longer balanced. We must balance the hydrogen!
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Practice 2H2 + O2 2H2O Count the atoms on each side. Reactant side:
4 atoms H 2 atoms O —Product side: 4 atoms H 2 atoms O
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Practice N2 + H2 NH3 Count the atoms on each side. Reactant side:
2 atoms N 2 atoms H —Product side: 1 atom N 3 atoms H
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Practice N2 + H2 2NH3 Count the atoms on each side. Reactant side:
2 atoms N 2 atoms H —Product side: 2 atoms N 6 atoms H
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Practice N2 + 3H2 2NH3 Count the atoms on each side. Reactant side:
2 atoms N 6 atoms H —Product side: 2 atoms N 6 atoms H
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