Reactions in Aqueous Solutions
Reactions in Aqueous Solutions
General Properties of Aqueous Solutions
An aqueous solution is a mixture of a pure solid or liquid (i.e. solute) in water (i.e. solvent)
There are 3 types of solutes in water:
1. Strong electrolytes:
- conductive in water
- usually ionic
- ions completely dissociate
$$\ce{ NaCl_{(s)} -> [H_2O] Na+_(aq) + Cl^- (aq) }$$
$$\ce{ NaCl_(s)}$$
Note: single arrow indicates complete dissociation
2. Weak electrolytes:
- poorly conductive
- usually molecular
- ions partially dissociate
$$ \ce{CH_3CO_2H_{(aq)} <=>[{H_2O}] CH_3CO^-2{(aq)} + H^+_{(aq)}}$$
Note: double arrow indicates reversible reaction, i.e. equilibrium
3. Non-electrolytes
- non-conductive
- always molecular
- dissolves but does not produce any ions
$$\ce{C12H22O11(s) ->[{H_2O}] C12H22O11(aq)}$$
Solubility Rules for Common Ionic Compounds in Water
Soluble Compounds
- Compounds of Alkali Metal Ions
- $\ce{ Li+, Na+, K+, Rb+, Cs+ }$
- Compounds of $\ce{ NH_{4}+ }$
- Nitrates ($\ce{ NO_{3}- }$)
- Acetates ($\ce{ C_{2}H_{3}O_{2}- }$)
- Chlorates ($\ce{ ClO_{3}- }$)
- Halides
- $\ce{ Cl-, Br-, I- }$
- Exceptions:
- Halides of $\ce{ Ag+, Hg^2+, Pb^2+ }$
- Sulfates ($\ce{ SO_{4}^2- }$)
- Exceptions:
- Sulfates of $\ce{ Ag+, Ca^2+, Sr^2+, Ba^2+ Hg^2+, Pb^2+ }$
- Exceptions:
Sparingly Soluble Compounds
- Carbonates ($\ce{ CO_{3}^2- }$), Phosphates ($\ce{ PO_{4}^3- }$), Chromates ($\ce{ CrO_{4}^2- }$)
- Exceptions:
- Compounds of alkali metal ions and $\ce{ NH_{4}+ }$
- Exceptions:
- Hydroxides ($\ce{ OH- }$), Sulfides ($\ce{ S^2- }$)
- Exceptions:
- Compounds of alkali metal ions and $\ce{ NH_{4}+ }$
- Sulfides of alkaline earth metal ions
- Hydroxides of $\ce{ Ba^2+ }$
- Exceptions:
Precipitation Reactions
A common type of reaction seen occurring in aqueous solutions is precipitation, which results in the formation of a sparingly soluble product, known as a precipitate.