Reactions and Periodicity: Rapid Review for AP Chemistry

By — McGraw-Hill Professional
Updated on Feb 1, 2011

For a more thorough review, refer to these concepts:

Rapid Review

  • Reactions will always occur in the free-response section of the AP exam. This may not be true in the multiple-choice part.
  • Energy may be released in a reaction (exothermic) or absorbed (endothermic).
  • Chemical equations are balanced by adding coefficients in front of the chemical species until the number of each type of atom is the same on both the right and left sides of the arrow.
  • The coefficients in the balanced equation must be in the lowest whole-number ratio.
  • Water is the universal solvent, dissolving a wide variety of both ionic and polar substances.
  • Electrolytes are substances that conduct an electrical current when dissolved in water; nonelectrolytes do not.
  • Most ions in solution attract and bind a layer of water molecules in a process called solvation.
  • Some molecular compounds, like acids, ionize in water, forming ions.
  • In the molecular equation, the reactants and products are shown in their undissociated/unionized form; the ionic equation shows the strong electrolytes in the form of ions; the net ionic equation drops out all spectator ions and shows only those species that are undergoing chemical change.
  • Precipitation reactions form an insoluble compound, a precipitate, from the mixing of two soluble compounds.
  • Learn and be able to apply the solubility rules.
  • Redox reactions are reactions where oxidation and reduction take place simultaneously.
  • Oxidation is the loss of electrons and reduction is the gain of electrons.
  • Oxidizing agents are reactants that cause oxidation to take place (the reactant being reduced), and reducing agents are reactant species that cause reduction to take place (the reactant being oxidized).
  • Combination reactions are usually redox reactions in which two or more reactants (elements or compounds) combine to form one product.
  • Decomposition reactions are usually redox reactions in which a compound breaks down into two or more simpler substances.
  • Single displacement reactions are redox reactions in which atoms of an element replace the atoms of another element in a compound.
  • Know how to use the activity series to predict whether or not an element will displace another element.
  • Combustion reactions are redox reactions in which the chemical species rapidly combine with diatomic oxygen gas, emitting heat and light. The products of the complete combustion of a hydrocarbon are carbon dioxide and water.
  • Indicators are substances that exhibit different colors under acidic or basic conditions.
  • Acids are proton donors (electron-pair acceptors).
  • Bases are proton acceptors (electron-pair donors)
  • Coordinate covalent bonds are covalent bonds in which one atom furnishes both of the electrons for the bond.
  • Strong acids and bases completely ionize/dissociate, and weak acids and bases only partially ionize/dissociate.
  • Know the strong acids and bases.
  • Acids react with bases to form a salt and usually water in a neutralization reaction.
  • Many hydrides react with water to form the hydroxide ion and hydrogen gas.
  • A titration is a laboratory procedure for determining the concentration of an unknown solution using a solution of known concentration.
  • The equivalence point of an acid–base titration is the point at which the moles of H+ from the acid equals the moles of OH from the base. The endpoint is the point at which the indicator changes color, indicating the equivalence point.
  • A complex ion is composed of a metal ion (Lewis acid) covalently bonded to two or more molecules or anions called ligands (Lewis base).
  • The coordination number (usually 2, 4, or 6) is the number of donor atoms that can surround a metal ion in a complex.
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