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.