Vocabulary
	chemical change combination reaction decomposition displacement double displacement isomerization neutralization precipitation product reactant redox synthesis

4 H2 + 4 Cl2		8 HCl

• Combination reactions build a compound from simpler compounds or elements.
  • General form: A + B C
  • Recognition: Usually a single product and several reactants
  • Synonyms: synthesis
  • Examples
    C₂H₄(g) + H₂O(g) C₂H₅OH(g)
    H₂(g) + ½ O₂(g) H₂O(l)
    
• Decomposition reactions break a compound into simpler fragments.

  4 H2O2		4 H2O + 2 O2

  • General form: C A + B
  • Recognition: Usually a single reactant and several products
  • Examples
    H₂CO₃(aq)H₂O(l) + CO₂(g)
    CaCO₃(s)CaO(s) + CO₂(g)
    2NH₄NO₃(s)2N₂(g) + 4H₂O(g) + O₂(g)
    2 H₂O(l) 2 H₂(g) + O₂(g)
• Rearrangement reactions making and breaking bonds within a compound.

  HOONO		HNO3

  • General form: A B
  • Recognition: reactant and product have same molecular formula but different structural formulas
  • Synonyms: isomerization
• Displacement reactions involve replacement or swapping of parts of a compound.
  • General forms
    • single displacement: A + BC AB + C
    • double displacement: AB + CD AD + BC
  • Features
    • # of reactants is usually equal to the # of products
      
    • atoms or ions migrate from one compound to another
  • Synonyms: double displacement reactions are sometimes called "metathesis" reactions
  • Examples
    Zn(s) + 2 HCl(aq)ZnCl₂(aq) + H₂(g)
    Mg(s) + CuCl₂(aq)MgCl₂(aq) + Cu(s)
    NaOH(aq) + HCl(aq) H₂O(l) + NaCl(aq)
    BaCl₂(aq) + Na₂SO₄(aq) = BaSO₄(s) + 2 NaCl(aq)
    

• Neutralization reactions: one compound acquires H⁺ from another
  • Features
    • usually double displacement reactions (but not always)
    • one reactant must be an acid (have detachable H⁺ ions)
    • one reactant must be a base (accept H⁺ taken from the acid)
    • water is a product if the base is a hydroxide
  • Synonyms: acid-base reaction, proton transfer reaction
  • Examples
    H₂SO₄(aq) + 2 NaOH(aq) Na₂SO₄(aq) + 2 H₂O(l)
    KOH + HC₂H₃O₂(aq) H₂O(l) + KC₂H₃O₂(aq)
    NH₃(aq) + HCl(aq) NH₄Cl(aq)
• Precipitation reactions: solid product is formed in a liquid or gaseous environment.
  • Features
    • usually displacement reactions that form an insoluble ionic compound
  • Examples
    AgNO₃(aq) + NaCl(aq) = AgCl(s) + NaNO₃(aq)
    SrCl₂(aq) + Na₂SO₄(aq) = SrSO₄(s) + 2 NaCl(aq)
    
• Redox reactions occur when one compound acquires electrons from another
  • Features
    • at least one reactant loses electrons
    • at least one reactant gains electrons
  • Examples
    
    • combustion reactions (fuel reacting with oxygen)
      2 C₂H₆(g) + 7 O₂(g) 4 CO₂(g) + 6 H₂O(g)
      
    • combination of elements 2 Na(s) + Cl₂(g) 2 NaCl(s)
      
    • displacement of hydrogen from water or acids 2 Na(s) + 2 H₂O(l) 2 NaOH(aq) + H₂(g)
      Zn(s) + 2 HCl(aq)ZnCl₂(aq) + H₂(g)
      
    • displacement of metal ions from solution
      Mg(s) + CuCl₂(aq)MgCl₂(aq) + Cu(s)
      Zn(s) + 2 AgNO₃(aq)Zn(NO₃)₂(aq) + 2Ag(s)
      

Copyright © 1997-2005 by Fred Senese
Comments & questions to fsenese@frostburg.edu
Last Revised 02/23/18.URL: http://antoine.frostburg.edu/chem/senese/101/reactions/types.shtml