Solutions

• Solutions


  • are homogeneous mixtures of two or more pure

  substances that can be varied in composition.

  • formed when solute is dispersed uniformly

  throughout the solvent.
• Solvent


  -present in greatest amount

  -substance in which a solute dissolves.
• Solute


  -other components present in the solution

  -the substance being dissolved
• Solubility


  The maximum amount of solute that can be

  dissolved in a given amount of solvent at a

  specific temperature.
• Solvation


  interaction between solute and solvent molecules

  due to IMFA.
• Hydration


  Solvation when solvent used is water
• Dilute


  a solution with low solute concentration.
• Concentrated


  a solution with high solute concentration.
• Saturated solution


  a solution that contains the maximum amount of solute that the solvent can dissolve at a given temperature. Additional solute will no longer dissolve if added.
• Unsaturated solution


  a solution containing amount of solute less than its solubility. It has the capacity to dissolve more solute.
• Supersaturated solution


  a solution containing an amount of solute greater than the solubility; an unstable solution.
• Classification of Solutions

  1. Based on Elemental Composition
  2. Based on Ionization Property of Solution
• Organic solutions


  solutions of compounds containing carbon except CO2 CO, carbonates, and cyanides.
• Inorganic solutions


  solutions of compounds of the other elements including acids, bases, and salts.
• Strong electrolytes


  substances which completely dissociates into ions.
• Weak electrolytes


  substances which produce small amounts of ions in solution; partially dissociated into ions.
• Nonelectrolytes


  substances that does not dissociate into ions; form nonconducting

  solutions.
• Three processes

  affect the energetics

  of solution:

  1. separation of solute particle
  2. separation of solvent particles
  3. new interactions between solute and solvent.
• Factors Affecting Solubility

  1. Nature of Solute and Solvent
  2. Temperature
  3. Density
• Temperature


  The solubility of gases decreases with increasing T.
• At higher T, gas molecules are moving more quickly. They have a higher tendency to find the surface and escape more quickly resulting to fewer gas molecules in the liquid.
• Pressure


  the solubility of a gas is increased as the pressure of the gas over the solvent increases. By contrast, the solubility of solids and liquids are not appreciably affected by pressure.
• Henry’s law


  the solubility of a gas is proportional to partial pressure of the gas above liquid. For gases, increasing the pressure increases solubility.
• Dilution


  When a solution is diluted, the volume is increased by adding more solvent, the concentration decreases, but the total amount of solute remains constant.
• Colligative Properties


  Changes in colligative properties depend only on the quantity of solute particles present, not on the kind of the solute particles.
• Among colligative properties 


  – Vapor pressure lowering

  – Boiling point elevation

  – Melting point depression

  – Osmotic pressure
• Freezing Point Depression


  Since the vapor pressure of the solution is lower than that of the solvent at any temperature, the solution freezes at a lower temperature than the solvent.
• Raoult’s law 


  the lowering of the freezing point of a dilute solution is directly proportional to the molal concentration of the solution.
• Boiling Point Elevation and Freezing Point Depression

  Nonvolatile solute-solvent interactions also cause solutions to have higher boiling points and lower freezing points than the pure solvent.
• Osmosis


  • Some substances form semipermeable membranes, allowing some smaller particles to pass through, but blocking other larger particles.

  • In biological systems, most semipermeable membranes allow water to pass through, but solutes are not free to do so.
• Osmotic Pressure


  The pressure required to stop osmosis, known as osmotic pressure
• hypertonic


  If the solute concentration outside the cell is greater than that inside the cell, the solution is
• Crenation


  Water will flow out of the cell
• hypotonic.


  If the solute concentration outside the cell is less than that inside the cell, the solution is
• hemolysis


  Water will flow into the cell
• Colloids


  Suspensions of particles larger than individual ions or molecules, but too small to be settled out by gravity are called
• Tyndall Effect


  Colloidal suspensions can scatter rays of light.