Ch. 8 Solutions

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Definitions

• solution: uniform mixture of one or more solutes in a solvent
  • All gas mixtures, gases/liquids/solids dissolved in liquid, and alloys form solutions
• concentration ($M\text{ (Molarity) }=\ce{mol/L}$): quantitative amount of solute in a solvent
• solubility ($\ce{g/L}$): maximum quantitative amount of solute that can be dissolved in a solvent
  • molar solubility: same thing but moles $\rightarrow \ce{mol/L}$
  • depends on temperature
• concentrated: large amount of solute dissolved in a solvent
• diluted: small amount of solute dissolved in a solvent
• saturated: maximum amount of solute dissolved in a solvent
• unsaturated: less than maximum amount of solute dissolved in a solvent
• supersaturated: more than maximum amount of solute dissolved in a solvent
  • accomplished by carefully cooling saturated solution; are metastable

Solubility

• all gases are soluble in each other, solids can be alloyed
• in general, liquid solutions can be made from solutes and solvents with similar polarity
  1. energy is used to separate solute particles
  2. energy is used to separate solvent particles
  3. energy is released to form new attractions between separated solute and solvent particles
  • solution formed when $E_\text{released} > E_\text{used} \rightarrow$ ultimately released as heat, increasing temperature
• entropy: states/arrangements a solute can have
  • increases greatly when solids are dissolved, moderately when liquids are dissolved, and almost none when gases are dissolved
  • increase in entropy aids solution process

Dissolution Rate

• heating, grinding, stirring all increase dissolution rate
• heating increases speed $\rightarrow$ increasing collisions
• grinding increases the surface area of exposure to the solvent
• stirring brings less-concentrated solvent in contact with the solute

Aqueous Solutions

when water is the solvent

• ionic compounds completely dissociate in water
• Strong Electrolytes: ionic compounds, $\ce{HCl}$, $\ce{HBr}$, and $\ce{HI}$ completely ionize; conducts electricity well
• Weak Electrolytes: partially ionize, most commonly weak acids/bases; results in an equilibrium; slightly conducts electricity
• Nonelectrolytes: dissolve, but do not form ions; does not conduct electricity