Balancing Chemical Equations

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Balancing Chemical Equations

• (hydrogen oxygen --gt water) This is a word
  equation.
• What does a word equation tell us?
• (2H2 O2 --gt2H2O) This is a symbolic equation.

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Balancing Chemical Equations

• What does a balanced symbolic tell us? Does it
  tell us more than the word equation?
• While a word equation tells us certain things, a
  balanced chemical equation tells us much more.

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Balancing Chemical Equations

• A BALANCED CHEMICAL EQUATION MUST SATISFY THE LAW
  OF CONSERVATION OF ATOMS. (total number of atoms
  of each element of reactants must equal total
  number of atoms of each element in products.)

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A Balanced Chemical Equation Tells us the
Following

• 1. Relative proportions of the reactants and the
  products.
• 2. Molecule to molecule ratios of all components
  of the reaction.
• 3. Mole to mole ratios of all components of the
  reaction.

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A Balanced Chemical Equation Tells us the
Following

• 4. Mass to mass of each substance in the
  reaction.
• 5. The ratios of masses of each substance in the
  reaction.
• 6. The reverse reaction.

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SYMBOLS

• Before we start we need to review some symbols
  and abbreviations. ( see page 246 in your text
  book)

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Factors in Equation Writing

• 1. The equation must represent the facts.
• 2. The equation must include all symbols used as
  reactants or products.
• 3. The law of conservation of atoms must be
  satisfied.

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SUBSCTRIPTS and COEFFICIENTS

• Subscripts are the numbers that are behind and
  below the symbol.
• Coefficients are in front of the symbol.
• There are different rules for the use of each one
  of these.

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BrINClHOF

• Remember that any time we have a BrINClHOF alone
  they require a 2 subscript

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WRITING BALANCED CHEMICAL EQUATIONS

• 1. Make sure that the equation represents the
  facts.
• 2. Write the correct formulas for compounds
  balanced as to oxidation number or charge.
• 3. Balance according to the law of conservation
  of atoms.

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EXAMPLES

• 1. water --gt hydrogen oxygen (remember the
  three steps)
• 2. Sulfur oxygen --gt sulfur dioxide
• 3. Mercury II oxide--gt mercury oxygen

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EXAMPLES CONT.

• 4. zinc hydrochloric acid ( HCl) --gt zinc
  chloride hydrogen
• 5. Aluminum sulfate calcium hydroxide --gt
  aluminum hydroxide calcium sulfate

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5 GENERAL TYPES OF CHEMICAL REACTIONS

• 1. COMPOSITION
• A X --gt AX
• element element --gt compound
• note there is only one product in this type of
  reaction

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EXAMPLE

• 1. Hydrogen oxygen --gt water
• 2. Iron sulfur --gt iron II sulfide
• 3. Magnesium oxygen --gt magnesium oxide

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5 TYPES OF CHEM.RXNS.

• 2. DECOMPOSITION
• AX --gt A X
• compound --gt element element
• note only one reactant in this type

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EXAMPLE

• 1. Water --gt hydrogen oxygen
• 2. Potassium chlorate --gt potassium chloride
  oxygen (This reaction is different. How?)

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5 TYPES OF CHEM. RXNS.

• 3. SINGLE REPLACEMENT
• A BX --gtAX B
• element compound --gt different compound
  different element

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EXAMPLE

• 1. iron copper II sulfate --gt iron II sulfate
  copper
• 2. copper silver nitrate --gt copper II nitrate
  silver

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5 TYPES OF CHEM. RXNS.

• 4. DOUBLE REPLACEMENT ( ionic) (square dance)
• AX BY --gt AY BX
• compound compound --gt different compound
  different compound

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EXAMPLE

• 1. sodium chloride silver nitrate --gt sodium
  nitrate silver chloride

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5 GENERAL TYPES OF CHEM. RXNS.

• 5.
• COMBUSTION
• hydrocarbon oxygen --gt water carbon dioxide
• Lets learn about hydrocarbons.