Chemistry 0010

Chemical Reactions

Topics you should learn:
1. Balancing Chemical Equations

   • Conventions and Symbols in Chemical Equations
   • Purpose of Balancing Chemical Equations
   • Methods of Balancing Chemical Equations

2. Types of Reactions

• Conventions and Symbols in Chemical Equations

  Take a look at the following example of a chemical equation.

  2 H2 (g) + O2 (g) --> 2 H2O (l)

  The following table summarizes the symbols and terms used in chemical equations:

  symbols/terms	meaning
  Reactants	what is written on the left-hand-side of the arrow. eg. H2 and O2
  Products	what is written on the right-hand-side of the arrow. eg. H2O
  -->	separates the reactants from the products
  (s),(l), (g)	indicates the physical states of each species in the chemical reaction. For example, (s) a solid substance , (l) a liquid substance, (g) a gaseous substance, (aq) an aqueous solution (substance dissolved in water)
  coefficients	are numbers written in front of each substance. If nothing is written in front, the default value is 1. eg. the 2 written in front of H 2 (g) is a coefficient. the 2 written in front of H2O (l) is a coefficient.

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  • Purpose of balancing chemical equations

    The purpose of balancing a chemical equation is to make sure that

    the number of atoms of each type on the LEFT-HAND-SIDE

    =

    the number of atoms of each type on the RIGHT-HAND-SIDE

    Why is this important? Remember the Law of Conservation of Mass?

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  • Methods of balancing chemical equations

    Many equations are easy to balance. But when you cannot see right away which atom you should start to balance first, try the following methods:

    1.	By inspection
    2.	By algebra

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  Read: 9-3 - Guidelines for Balancing Chemical Equations (page 219) 9-4 - Examples Involving Balancing Equations (page 221)

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  Send Comments to Rosamaría Fong.

  

  Types of Reactions

  Most chemical reactions can be placed into one or more of the five categories:

  Combination Reactions	A + B --> AB
  Decomposition Reactions	AB --> A + B
  Single-Replacement Reactions	A + BC --> AC + B
  Double-Replacement Reactions	AB + CD --> AD + CB
  Neutralization Reactions	HX + MOH --> MX + HOH

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  You will be expected to be able to:

  • classify reactions into these five types of reactions,
  • use the activity series of metals to predict products of reactions,
  • apply solubility rules to predict the products of reactions.
  • know combustion reactions involve reaction with oxygen, O₂ (g),
  • know combustion of compounds containing C, H,(and O) yield CO₂ (g) and H₂O (l),
  • know neutralization of an acid with a base yields a salt and water.

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  Read: 9-5 - The Five Simple Types of Chemical Equations (page 224) 9-6 - Combination Reactions (page 224) 9-7 - Decomposition Reactions (page 226) 9-8 - Single-Replacement Reactions. The Electromotive or Activity Series (page 227) 9-9 - Double-Replacement Reactions. Rules for the Solubility of Inorganic Substances in Water (page 230) 9-10 - Neutralization Reactions (page 234)

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  Send Comments to Rosamaría Fong.

  

  Rosamaría Fong, Instructor of Chemistry,
  British Columbia Institute of Technology, Burnaby, B.C. Canada.
  

  

  Send Comments to Rosamaría Fong.

  All contents copyrighted © 1996
  Rosamaría Fong, Instructor of Chemistry
  All Rights reserved
  
  : Last updated on June 16, 1996