Introduction to Aqueous Solutions Notes
Most interesting chemical reactions happen in aqueous solutions. Review how a solutions are formed. (A
solute is dissolved in a solvent.) Review that both solutions have a concentration, which is a numeric
reflection of the moles of solute compared to the volume of solution (M or moles/litre). It may also be
necessary to review stoichiometry. A solution may be diluted using the formula: M1V1 = M2 V2,, which
assumes that the moles of solute remain constant while the volume of solution is changing. When two
aqueous solutions are mixed together, a precipitate reaction may or may not occur. The precipitate
produced by the reaction is insoluble, or slightly soluble, in the aqueous product. In order to predict if a
precipate reaction will occur, solubility rules are referenced.
Solubility: is understood as a maximum amount of solute that dissolves in a solvent at so called
equilibrium. In chemistry, an equilibrium is a state where reactants and products reach a balance - no
more solute can be dissolved in the solvent in the constant conditions (i.e., temperature, pressure). Such
a solution is called a saturated solution.
Precipitation: is the formation of a solid in a solution or inside another solid during a chemical reaction
or by diffusion in a solid. When the reaction occurs in a liquid, the solid formed is called the precipitate,
or when compacted by a centrifuge, a pellet. The liquid remaining above the solid is in either case called
the supernate or supernatant.
Example 1: NaCl(s) dissolved in water
Simulation: http://phet.colorado.edu/en/simulation/soluble-salts
Molecular level (diagram):
Symbolic level (formula):
Example 2: NaCl(aq) + AgNo3(aq) combined together
Go to simulation for precipitation (double displacement) reaction between silver nitrate and sodium
chloride: http://www.crescent.edu.sg/crezlab/Webpages/PptReaction4.htm#
Molecular Level:
Symbolic Level: