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Balancing Chemical Equations
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Law of Conservation of Mass
To follow the Law of Conservation of Mass, we must have the same number of atoms of each element on both sides of the equation.
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Balanced Chemical Equations
C + O2 CO2 This is balanced!! 1 C and 2 O on each side of the equation. H2 + O2 H2O This is not balanced!! 2 H’s on both the right and the left of the arrow, but 2O’s on the left and only 1 O on the right.
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How to Balance Chemical Equations
To balance an equation we change coefficients, but never the subscripts. Coefficient - large numbers in front of the compound. This tells us how many atoms or molecules are taking place in the reaction. H2 + O2 H2O The balanced equation: 2 H2 + O2 2 H2O
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Balancing Chemical Equations
1 To balance an equation: 2 Determine your equation. If this part is not correct, your equation will never balance. 3 Create a chemical inventory of the elements then count the atoms. Consider polyatomic ions to be a unit if it is on both sides of the equation – like OH or PO4. 4 Balance the elements one at a time using coefficients. When there is no coefficient, we assume it to be one, just like subscripts. You can NEVER change the subscripts in a chemical equation!!! 5 Check each atom so all are balanced. Equal on each side!!! 6 All the coefficients should be in the lowest possible ratio.
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Balancing Chemical Equations
Silver nitrate and copper metal combine to form copper (II) nitrate and silver metal. AgNO3 + Cu Cu(NO3)2 + Ag 1 Ag 1 1 NO3 2 1 Cu 1 Balance by changing coefficients: 2 AgNO3 + __Cu __Cu(NO3)2 + 2 Ag
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Balancing Chemical Equations
Carbon monoxide combines with iron (III) oxide to form iron metal and carbon dioxide. CO + Fe2O3 Fe + CO2 1 C 1 2 Fe 1 4 O 2 Balance by changing coefficients: 3 CO + __Fe2O3 2 Fe + 3 CO2
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