Aqueous Chemistry and Solutions

Concentration and Molarity

• Concentration: Amount of solute divided by amount of solvent or solution.

• Molarity ($M$): Defined as moles of solute per liter of solution.

  • Symbol: Capital $M$.

  • Acts as a conversion factor (moles/liter or liter/moles).

Preparing Solutions

• Process: Dissolve a calculated mass of solute in sufficient water to achieve the desired total solution volume ($V$).

Dilution

• Process of reducing a solution's concentration by adding more solvent (typically water).

• Formula: C1V1 = C2V2$(where$C$is concentration and$ V is volume).

• Moles of solute are conserved during dilution.

• Important: This formula is exclusively for dilution problems, not stoichiometry.

Dissolving Processes

• Covalent Compounds (e.g., sugar, alcohol): Disperse in water but do not ionize.

• Ionic Compounds: Water 'separates' ionic compounds into individual ions.

• Acids:

  • Strong Acids: Completely ionize in water (all hydrogen atoms are lost as ions).

  • Weak Acids: Partially ionize in water (only some hydrogen atoms are lost as ions).

• Polyatomic Ions: Remain intact as a single unit when dissolved; they do not further dissociate (e.g., $SO<em>4^{2-}$, $NO</em>3^{-}$).

Electrolytes

• Substances that form ions in solution and conduct electricity.

• Pure water: A poor conductor of electricity.

• Pure ionic compound (solid): A poor conductor of electricity.

• Aqueous ionic compound solution (e.g., salt water): A good conductor of electricity.

Solubility Rules and Equations

• Not all ionic compounds are soluble in water; solubility rules predict this.

• Equation Types:

  • Molecular Equation: A balanced chemical equation showing complete formulas and phase scripts ($(s)$, $(l)$, $(g)$, $(aq)$).

  • Total Ionic Equation: Shows all soluble ionic compounds as their dissociated ions.

  • Net Ionic Equation: Represents only the species directly involved in the chemical change, excluding spectator ions.

• Spectator Ions: Ions present in the solution that do not participate in the chemical reaction.

Types of Reactions

• Precipitation Reactions: Occur when two aqueous solutions are mixed, leading to the formation of an insoluble solid (precipitate).

• Acid-base reactions are also covered.