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Chemical equation the symbolic representation of a chemical reaction (process) wherein thechemical reaction reactantreactant entities are on left side and change into productproduct entities on right-hand side

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Chemical Equation Symbols The arrow can be read as “yields” or “produces” The + sign reads as “and” or “plus”

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Chemical Equation Symbols The arrow can be read as “yields” or “produces” Coefficients are the numbers in front of the formulas Coefficients can be changed to balance chemical equations Subscripts tell us how many atoms or molecules we have NEVER change subscripts when balancing chem. equations

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Balancing Equations like solving a puzzle Br 2 + Al Al 2 Br 6 (not balanced) Balance using coefficients

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Balancing Equations Reactants Products O 2 + H 2 H 2 O

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Balancing Equations Reactants Products O 2 + H 2 H 2 O but this equation is not balanced why not?

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Balancing Equations Conservation of Mass- Mass and/or Atoms are not Created or Destroyed during a chemical reaction. There must be the Same number of atoms on each side of the equation to balance the chemical equation.

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Steps to Balance Chemical Equations 1.Write unbalanced equation. 2.Count # atoms on each side. 3.Add coefficients to make #s of atoms equal. Coefficient subscript = # of atoms 4.If necessary reduce coefficients to lowest possible ratio (never change subscripts) 5.Update and Double check atom balance!!!

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Balancing Equations Step 1. Write unbalanced equation O 2 + H 2 H 2 O

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Balancing Equations Step 2. Count # of atoms on each side O 2 + H 2 H 2 O O = 2 0 = 1 H = 2

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Balancing Equations 3. Add coefficients to make # of atoms = on each side O 2 + H 2 H 2 O O = 2 0 = 1 H = 2

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Balancing Equations 3. Add coefficients to make # of atoms = on each side O H 2 2 H 2 O O = 2 0 = 2 H = 4

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Balancing Equations 4. If necessary find lowest ratio (never change subscripts) O H 2 2 H 2 O O = 2 0 = 2 H = 4

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Balancing Equations 5. Update and double check work O H 2 2 H 2 O O = 2 0 = 2 H = 4

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Balancing Steps 1.Write the unbalanced equation. Al + CuCl 2 Cu + AlCl 3

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Balancing Steps 1.Write the unbalanced equation. 2.Count atoms on each side. Al + CuCl 2 Cu + AlCl 3 1 Al 1 1 Cu 1 2 Cl 3

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Balancing Steps 1.Write the unbalanced equation. 2.Count atoms on each side. 3.Add coefficients to make #s equal. Coefficient subscript = # of atoms Al + CuCl 2 Cu + AlCl 3 1 Al 1 1 Cu 1 2 Cl 3

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Balancing Steps 1.Write the unbalanced equation. 2.Count atoms on each side. 3.Add coefficients to make #s equal. Coefficient subscript = # of atoms Al + 3 CuCl 2 Cu + 2 AlCl 3 1 Al 2 3 Cu 1 6 Cl 6

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Balancing Steps 1.Write the unbalanced equation. 2.Count atoms on each side. 3.Add coefficients to make #s equal. Coefficient subscript = # of atoms 2 Al + 3 CuCl 2 3 Cu + 2 AlCl 3 2 Al 2 3 Cu 3 6 Cl 6

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Balancing Steps 1. Write the unbalanced equation. 2.Count atoms on each side. 3.Add coefficients to make #s equal. Coefficient subscript = # of atoms 4.Reduce coefficients to lowest possible ratio, if necessary. 5.Double check atom balance!!!

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Helpful Tips Balance one element at a time. Balance most complicated compound first! Update ALL atom counts after adding a coefficient. Balance (polyatomic ions) as (single units). –“1 SO 4 ” instead of “1 S” and “4 O” Balance most complicated compound first, balance oxygen and hydrogen last (MINOH metals, ions, non-metals, oxygen, hydrogen ) Ask yourself this question what am I forced to do to balance the equation???

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Examples ____ Mg + ____ O 2 ____ MgO

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Examples 2 Mg + O 2 2 MgO

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Examples ____ Al + ____ S ____ Al 2 S 3

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Examples 2 Al + 3 S Al 2 S 3 ____ C 3 H 8 +____ O 2 ____ CO 2 + ____ H 2 O

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Examples 2 Al + 3 S Al 2 S 3 C 3 H O 2 3 CO H 2 O

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More Examples ___ Al +____ H 2 SO 4 ____Al 2 (SO 4 ) 3 +____ H 2

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More Examples 2 Al + 3 H 2 SO 4 Al 2 (SO 4 ) H 2

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Helpful Tips Balance one element at a time. Update ALL atom counts after adding a coefficient. Balance (polyatomic ions) as (single units). –“1 SO 4 ” instead of “1 S” and “4 O” Balance most complicated compound first, balance oxygen and hydrogen last Ask yourself this question what am I forced to do to balance the equation???

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