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Chemical Reactions

Chemical Reactions. Chemical Changes, Equations, and Reactions. Vocabulary. Cation – An ion with a positive charge. This means that it is “lacking” in electrons. Anion – An ion with a negative charge. This means that it has too many electrons.

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Chemical Reactions

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  1. Chemical Reactions Chemical Changes, Equations, and Reactions

  2. Vocabulary • Cation – An ion with a positive charge. This means that it is “lacking” in electrons. • Anion – An ion with a negative charge. This means that it has too many electrons. • Reactants – The substances in a chemical reaction that react. These appear BEFORE the yield arrow. • Products – The substances in a chemical reaction that are produced. These appear AFTER the yield arrow.

  3. Father of Chemistry • Lavoisier is considered the “Father of Chemistry.” • He contributed (among other things) the Law of Conservation of Mass. • Conservation of Mass – The total mass BEFORE a reaction must equal to the total mass AFTER the reaction. • He also started the first nomenclature of chemistry. This includes the symbols and the language of chemistry that we still use today.

  4. Chemical Equations • Chemical Equations show or represent the reactants and products in a reaction. These include the chemical compounds and their coefficients. • Coefficients – the number of units of each substance taking part in a reaction. • Chemical Equations must be balanced. This is to adhere to the law of conservation of mass.

  5. Reactions • Metals react with the atmosphere. • When iron is exposed to air and moisture, it corrodes or rusts. • When copper is exposed to air, it forms a blue-green coating called patina.

  6. Combustion Reaction • Combustion Reaction – this occurs when a substance reacts with oxygen to produce energy in the form of heat and light. If it burns, it is a combustion reaction. NOTE: oxygen must be one of the reactants or a component of one of the reactants.

  7. Synthesis Reaction • A synthesis reaction is when two or more substances combine to form another substance. • General Form: A + B  AB

  8. Decomposition Reaction • A decomposition reaction occurs when one substance breaks down or decomposes into two or more substance. Most require the use of heat, light, or electricity. • General Formula: AB  A + B

  9. Single Displacement Reaction • A single displacement reaction occurs when one element replaces another element in a compound. • General Formula: A + BC  AC + B Mg + 2H2O  Mg(OH)2 + H2

  10. Double Displacement Reaction • In a double displacement reaction, the positive ion of one compound replaces the positive ion of the other to form two new compounds. • General Formula: AB + CD  AD + CB Pb(NO3)2 + 2KI  PbI2 + 2KNO3

  11. Oxidation-Reduction Reaction • Oxidation-reduction reactions involve the transfer of electrons between species. This includes an oxidation reaction (gaining of electrons) and also a reduction reaction (loss of electrons) – sometimes called redox. • Oxidation: Cu(s)  Cu+2(aq) + 2e- • Reduction: 2Ag+(aq) + 2e-  2Ag(s) • Oxidation-reduction reaction: Cu(s) + 2Ag+(aq) + 2e-  Cu+2(aq) + 2Ag(s) + 2e- Or Cu(s) + 2Ag+(aq)  Cu+2(aq) + 2Ag(s)

  12. Mr. Gabel’s Guide to ID Reactions • Step 1: Does it have oxygen as a reactant and carbon dioxide and water as a product? If yes, combustion! • Step 2: Does it have two or more compounds that form one chemical? If yes, synthesis! • Step 3: Does it have one large molecule that falls apart into smaller ones? If yes, decomposition! • Step 4: Does it have a molecule that contains only one element? If yes, single displacement! • Step 5: Do the molecules exchange elements? If yes, double displacement! • Step 6: Any other would be redox.

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