Chemical Formulae, Types of Reactions, Chemical Equations, and Balancing

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Chemical Formulae, Types of Reactions,Chemical
Equations,and Balancing
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Chemical Formulae

• Indicates the of atoms of each type in a
  molecule or the ratio of the of atoms of each
  type in a compound

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• Worksheet to practice writing chemical formulae

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Types of Chemical Reactions

• Chemical reactions are chemical changes in which
  new substances are formed.

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Synthesis Reaction

• 2 or more simple substances combine to form a
  more complex substance
• These reactions come in the general form of
  A B ---gt AB

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Eg. Synthesis Reaction

• Hydrogen gas combined with oxygen gas can produce
  a more complex substance ? water!
• The chemical equation for this synthesis reaction
  looks like 2H2 O2 ? 2H2O
• Reactant reactant ? product

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Decomposition Reaction

• A more complex substance breaks down into its
  more simple parts. One reactant yields 2 or more
  products.
• These reactions come in the general form
• AB ---gt A B

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Eg. Decomposition Reaction

• Water can be broken down into hydrogen gas and
  oxygen gas. The chemical equation for this
  decomposition reaction looks like 2H2O ? 2H2
  O2 reactant ? product product

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Single Replacement Reaction

• A single uncombined element replaces another in a
  compound. Two reactants yield two products.
• These reactions come in the general form of A
  BC ---gt AC B

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Eg. Single Replacement Reaction

• Zinc combines with hydrochloric acid, the zinc
  replaces hydrogen. The chemical equation for this
  single replacement reaction looks like
• Zn 2HCl ? ZnCl2 H2
• reactant reactant ? product product

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Double Replacement Reaction

• Parts of two compounds switch places to form two
  new compounds. Two reactants yield two products.
• These reactions are in the general form
• AB CD ---gt AD CB

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Eg. Double Replacement Reaction

• Silver nitrate combines with sodium chloride, two
  new compounds - silver chloride and sodium
  nitrate are formed because the sodium and silver
  switched places. The chemical equation for this
  double replacement reaction looks like AgNO3
  NaCl ? AgCl NaNO3
• reactant reactant ? product
  product

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Combustion

• Oxygen combines with another compound to form
  water and carbon dioxide.
• Eg. CH4(g) 2O2(g) ? 2H2O(g) CO2(g)

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Acid - Base

• Acid and base react with each other. The H ion
  in the acid reacts with the OH- ion in the base,
  causing the formation of water.
• The product of this reaction is salt and water
  HA BOH ---gt H2O BA

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Eg. Acid - Base

• Reaction of hydrochloric acid and sodium
  hydroxide to form sodium chloride and waterHCl
  NaOH ---gt NaCl H2O

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• Questions to review 6 types of reactions
• Possibly get students to work in groups to learn
  types of reactions
• Matching questions definition of each reaction,
  match up to an example

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Chemical Equations

• A way of writing the changes in a chemical
  reaction
• Reactants combine and produce new chemical
  substances products
• Reactants ? Products
• The and type of atoms in the reactants should
  always be equal to the and type of atoms in the
  products

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Chemical Equations Contd

• H2(g) O2(g) ? H2O(l) 2H2(g) O2(g) ?
  2H2O(l)
• 2 2 2 1 4 2
  4 2
• Symbols in brackets state
• s solid
• l liquid
• g gas
• aq aqueous

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Balancing Chemical Equations!

• Balanced chemical equations tells you the ratio
  in which the elements are combined and produced
• A chemical equation is balanced when the number
  of atoms of each type on each side of the
  equation is the same.

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How to Balance an Equation

• Start with word equation and name reactants and
  products
• Eg. methane gas oxygen gas ? carbon dioxide
  water
• Replace the words with formulae and rewrite
  equation
• Eg. CH4 O2 ? CO2 H2O
• Count atoms of each element
• Element Reactants Products
• C 1 1
• H 4
  2
• O 2
  3
• If atoms on both sides are not equal, need to
  balance the equation
• Eg. CH4 2O2 ? CO2 2H2O
• Add physical state symbols
• Eg. CH4(g) 2O2(g) ? CO2(g) 2H2O(l)

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• Worksheet with balancing equation questions