AP Chemistry Unit 2
Ionic Theory of Solution
Certain substances produce freely moving ions when dissolved in water,
creating an aqueous solution that can conduct an electric current. Electrolyte­ dissolves in water to give an electrically conducting solution
Ionic solids = Yes!
Molecular compounds that dissolve into ions = Yes!
(strong acids for example)
Nonelectrolyte­ dissolves in water to give a nonconducting solution
Molecular compounds mixing with molecular water
(sugar, methanol for example)
"Strong" vs. "Weak"
Strong­ exists almost entirely as ions
NaCl (s)
H 2O
Na1+ (aq) + Cl1­ (aq)
Weak­ very small percentage of ions, typically molecular compounds (HCl, stong acids = exceptions)
NH3 (aq) + H2O (l)
Ionic Theory of Solution/Precipitation
reverse!
NH41+ (aq) + OH1­ (aq)
about 3%
AP Chemistry Unit 2
We use chemical equations to describe chemical reactions. There are different types:
Molecular: "regular" equation: everything is written as if they are molecules, even if they might exist in solution as ions
Ba(OH)2 (aq) + K2CO3 (aq)
BaCO3 (s) + 2 KOH(aq)
Complete Ionic: ionic theory interpretation of the molecular equation
Ba2+ (aq) + 2 OH1­ (aq) + 2 K1+ (aq) + CO32­ (aq)
BaCO3 (s) + 2 K1+ (aq) + 2 OH1­ (aq)
Spectator ions: ions not taking part in the reaction
Net Ionic: a complete ionic equation with the spectator ions cancelled out: shows what is actually happening at the particle (ion) level
*weak electrolytes stay as molecules, insolubles stay as solids
Ba2+ (aq) + CO32­ (aq)
Ba(NO3)2 (aq) + Na2CO3 (aq)
BaCO3 (s)
BaCO3 (s) + 2 NaNO3(aq)
Ba2+ (aq) + 2 NO31­ (aq) + 2 Na1+ (aq) + CO32­ (aq)
BaCO3 (s) + 2 Na1+ (aq) + 2 NO31­ (aq)
Ionic Theory of Solution/Precipitation
AP Chemistry Unit 2
Precipitation Reactions
Precipitate: an insoluble solid compound formed during a chemical reaction in solution
Precipitation Reactions
How can you tell if one will occur?
If it does, what products should you expect?
As a molecular equation, they take the form of a METATHESIS (exchange) reaction: appears to involve the exchange of parts between reactants
Double Displacement/Replacement
BaCl2 + AgNO3
BaCl2 + 2 AgNO3
2 AgCl + Ba(NO3)2
How will this play out on the particle level?
Complete Ionic:
Net Ionic:
Ionic Theory of Solution/Precipitation