MA

Chapter 9: Solutions

9.1: Solutions

  • Solution: A homogeneous mixture in which the solute formly dispersed in a solvent.
  • Water (H20): It is one of the most common solvents in nature.
    • It is polar, thus it is a polar solvent.
  • Solutes and solvents may be solids, liquids, or gases.
    • The solution that forms has the same physical state as the solvent.
  • Hydrogen Bonds: Occur between molecules where partially positive hydrogen atoms are attracted to the partially negative atoms.
  • Hydration: The process of surrounding dissolved ions by water molecules.

9.2: Electrolytes and Non-electrolytes

  • When electrolytes dissolve in water, the process of dissociation separates them into ions forming solutions that conduct electricity.
  • When nonelectrolytes dissolve in water, they do not separate into ions and their solutions do not conduct electricity.
  • Strong electrolyte: There is 100% dissociation of the solute into ions.
  • Weak Electrolyte: A compound that dissolves in water mostly as molecules.
  • Equivalent (Eq): The amount of that ion equal to 1 mole of positive or negative electrical charge.
  • In any solution, the charge of the positive ions is always balanced by the charge of the negative ions.

9.3: Solubility

  • It is the maximum amount of solute that can be dissolved at a certain temperature.
  • It is used to describe the amount of a solute that can dissolve in a given amount of solvent
  • It is usually expressed in grams of solute in 100 g of solvent.
  • Unsaturated solution: The solution does not contain the maximum amount of solute.
  • Saturated solution: A solution that contains all the solutes that can dissolve.
  • Recrystallization: A process that occurs when a solution is saturated, the rate at which the solute dissolves becomes equal to the rate at which the solid forms.
  • When a saturated solution is carefully cooled, it becomes a supersaturated solution because it contains more solute than the solubility allows.
  • Henry’s Law: It states that the solubility of a gas in a liquid is directly related to the pressure of that gas above the liquid.
  • Soluble Salts: Ionic compounds that dissolve in water.
  • Insoluble Salts: Ionic compounds that do not dissociate into ions in water.

9.4: Concentrations of Solutions

  • Concentration: The amount of solute dissolved in a certain amount of solution.

  • Mass percent (m/m): The mass of the solute in grams for exactly 100 g of solution.

  • Volume Percent (v/v): The concentration of the volume of liquids or gases.

  • Mass/volume percent: The mass of the solute in grams for exactly 100 mL of solution.

  • Molarity (M): A concentration that states the number of moles of solute in exactly 1 L of solution.

9.5: Properties of Solutions

  • Dilution: A solvent is added to a solution, which increases the volume.
  • Solution
    • It appears transparent, although it may have a color.
    • The particles are so small that they go through filters and through semipermeable membranes.
    • A semipermeable membrane allows solvent molecules such as water and very small solute particles to pass through but does allow the passage of large solute molecules.
  • Colloidal particles
    • These are large molecules, such as proteins, or groups of molecules or ions.
    • These are small enough to pass through filters but too large to pass through semipermeable membranes.
  • Suspension
    • These are heterogeneous, nonuniform mixtures that are very different from solutions or colloids.
    • The particles of these are so large that they can often be seen with the naked eye.
  • Osmosis
    • The water molecules move through a semipermeable membrane from the solution with the lower concentration of solute into a solution with a higher solute concentration.
    • Osmotic Pressure: It prevents the flow of additional water into the more concentrated solution.
    • Reverse Osmosis: A pressure greater than the osmotic pressure is applied to a solution so that it is forced through a purification membrane.
  • Isotonic Solutions: A solution that has the same particle concentration and osmotic pressure as that of the cells of the body.
  • Hypotonic Solutions: A solution that has a lower particle concentration and lower osmotic pressure than the cells of the body.
    • Hemolysis: The increase in fluid causes the cell to swell, and possibly burst.
  • Hypertonic Solutions: A solution that has a higher particle concentration and higher osmotic pressure than the cells of the body.
    • Crenation: A process when the water leaves the cell, it shrinks.
  • Dialysis
    • A dialyzing membrane, permits small solute molecules and ions as well as solvent water molecules to pass through, but it retains large particles, such as colloids.
    • It is a way to separate solution particles from colloids.