AQUEOUS REACTIONS

  • A solution is a homogeneous mixture of two or more substances.
  • All aqueous solutions can be classified in terms their ability to conduct electricity.
  • If a substance forms ions in solution, it is an electrolyte and will conduct electricity. Ie. NaCl
  • If a substance does not form ions in solution, it is a nonelectrolyte and does not conduct electricity.Ie. sugar
  • Compounds whose aqueous solutions conduct electricity well are strong electrolytes. Compounds whose solutions conduct electricity poorly are weak electrolytes.
  • Exchange (metathesis) reactions involve the exchange of ions in solution.
  • Ionic equations: 2KI(aq)+Pb(NO3)2(aq)PbI2(s)+2KNO3(aq)
  • Both potassium iodide and lead nitrate are colorless solutions. When mixed they form lead iodide, a yellow precipitate.
  • The molecular equation lists all species in their molecular form
  • The complete ionic equation lists all strong soluble electrolytes as ions:Pb2+(aq)+2NO3-(aq)+2K+(aq)+2I-(aq)PbI2(s)+2K+(aq)+2NO3-(aq)
  • The net ionic equation lists only those ions not common on both sides of the reaction:Pb2+(aq)+2I-(aq)PbI2(s)
  • The spectator ions that are present in the solution , but play no direct role in the reaction are eliminated in the net equation.
  • Acids are substances that ionize in aqueous solutions to form H+. Acids are proton donors. Bases are proton acceptors. Bases react with the H+ to form water.
  • Strong acids and bases are strong electrolytes. They ionize completely in solution.
  • Strong bases include Group1A metal hydroxides, Ca(OH)2, Ba(OH)2, and Sr(OH)2
  • Strong acids include HCl, HBr, HI, HClO3, H2SO4, and HNO3
  • Weak acids and weak bases are weak electrolytes. They partially ionize in solution.
  • A neutralization reaction occurs when an acid and base react. The result is the formation of a salt and water
  • Acids react with carbonates and hydrogen carbonates to form carbon dioxide and water
  • H+(aq)+ HCO3-(aq)H2O(l)+CO2(g)
  • Reaction of sulfides with acid generate hydrogen sulfide
  • 2H+(aq)+S2+(aq)H2S(g)
  • When a substance loses electrons, it undergoes oxidation(OIL): Ca(s)+2H+(aq)Ca2+(aq)+H2(g).
  • When a substance gains electrons, it undergoes reduction(RIG): 2Ca(s)+O2(g)2CaO(s)
  • The reaction of a metal with an acid or a metal salt is called a displacement reaction: A+BXAX+B
  • It is common for metals to produce hydrogen gas when they react with acids.
  • Mg(s)+2HClMgCl2(aq)+H2(g) molecular
  • Mg(s)+2H+Mg2+(aq)+ H2(g) net ionic
  • The metal is oxidized and the H+is reduced.
  • It is possible for metals to be oxidized in the presence of a salt:Fe(s)+Ni(NO3)2(aq)Fe(NO3)2(aq)+Ni(s) molecular
  • Fe(s)+ Ni2+(aq)Fe2+(aq)+Ni(s) net ionic
  • In this case, iron is oxidized and nickel is reduced.
  • If one substance is oxidized, another substance must be reduced.
  • Molarity=moles of solute/liters of solution
  • When an ionic compound dissolves, the relative concentration of ions depends on the chemical formula
  • For 1M NaCl, the solution is 1M in Na+ ; 1M in Cl-
  • For 1M Na2SO4, the solution is 2M in Na+; 1M in SO4-
  • When making dilutions, MinitialVinitial=MfinalVfinal