Chemical Reactions

• Chemical Reaction


  A process in which one or more substances are converted into one or more new substances
• Chemical equation


  A shorthand notation to describe a chemical reaction
• Chemical equation


  • Reactants on left side
  • Products on right side
  • Relative amounts using stoichiometric coefficients
• Reactant(s)


  Substances that undergo a chemical change
• Product(s)


  Substances formed from a chemical reaction
• Balanced chemical equations must always include the same number of each kind of atom on both sides of the equation
• There is no detectable change in quantity of matter in an ordinary chemical reaction
• Types of reactions in Aqueous Solutions

  • Non-RedOx Reactions
  • Precipitation Reactions
  • Neutralization Reactions
  • Oxidation-Reduction (RedOx) Reactions
  • Combination/Synthesis
  • Decomposition
  • Single Displacement Reactions
• Precipitation Reaction


  Many ionic compounds are soluble in water; if two of the ions combine to form a water-insoluble compound, a precipitate forms
• Precipitation Reaction Example


  • AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)
• Precipitation Reaction Ionic Equation


  • Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq) → AgCl(s) + Na+(aq) + NO3-(aq)
• Precipitation Reaction Net Ionic Equation

  • Ag+(aq) + Cl-(aq) → AgCl(s)
• Molecular (Formula) Equation


  Gives the overall reaction stoichiometry but not necessarily the actual forms of the reactants and products in solution
• Reactants and products generally shown as compounds in a molecular equation
• Complete Ionic Equation


  Represents as ions all reactants and products that are soluble in water
• Spectator ions


  Appear unchanged on both sides of a chemical equation
• Na+ and NO3- are spectator ions
• Net Ionic Equation


  Includes only the ions that react (no spectator ions are shown)
• Formation of silver chloride, AgCl (white precipitate)
• Neutralization Reaction


  A reaction between an acid and a base; proton-transfer reaction
• Neutralization Reaction Example 1

  • Na2O(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l)
• Neutralization Reaction Example 2

  • MgO(s) + HNO3(aq) → Mg(NO3)2(aq) + H2O(l)
• Neutralization Reaction Example 3

  • Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + CO2(g) + H2O(l)
• Neutralization Reaction Example 4

  • NaHCO3(s) + HCl(aq) → NaCl(aq) + CO2(g) + H2O(l)
• Neutralization Reaction Example 5


  • NH3(aq) + HCl(aq) → NH4Cl(aq)
• Reduction-Oxidation Reaction


  A reaction in which electrons are transferred from one species to another
• Oxidation state (oxidation number)


  It provides a way to keep track of electrons in oxidation-reduction reaction
• Free elements (uncombined state) have an oxidation number of zero
• In monatomic ions, the oxidation number is equal to the charge on the ion
• The oxidation number of oxygen is usually –2 (except O2^2- where it is –1)
• The oxidation number of hydrogen is +1 (except when it is bonded to metals in binary compounds where it is –1)
• The sum of the oxidation numbers of all the atoms in a molecule or ion is equal to the charge on the molecule or ion
• Reduction-Oxidation Reaction Example


  • Zn(s) + Cu^2+(aq) → Zn^2+(aq) + Cu(s)
• Oxidizing agent


  A substance that gains electrons in a redox reaction
• Reducing agent

  A substance that loses electrons in a redox reaction
• Identify oxidizing and reducing agents in redox reactions

  • Cl2(g) + KBr(aq) → Br2(g) + KCl(aq)
  • Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq) + 2Ag(s)
• Types of RedOx Reaction

  • Combination Reaction
  • Decomposition Reaction
• Activity series of halogens: F2 > Cl2 > Br2 > I2
• An alternative definition of oxidation-reduction is: oxidation: The gain of oxygen and/or loss of hydrogen; reduction: The loss of oxygen and/or gain of hydrogen