Ch 6

• Concentration

  Amount of solute dissolved in a given amount of solution
• Concentration of a solution

  • Has an effect on physical properties
  • Has an effect on chemical properties
• Mass/Volume Percent

  • Amount of solute = mass of solute in grams
  • Amount of solution = volume in milliliters
  • Concentration is expressed as a percentage by multiplying ratio by 100%
• Mass/Mass Percent

  Most useful for solutions of 2 solids whose masses are easily obtained
• Parts Per Thousand (ppt) and Parts Per Million (ppm)


  • As percentage is the number of parts of solute in 100 parts of solution, ppt and ppm change the calculation only by orders of magnitude
  • ppt and ppm are most often used for very dilute solutions
• Chemical equations represent the relative number of moles of reactants producing products
• Many chemical reactions occur in solution where it is most useful to represent concentrations on a molar basis
• Molarity

  • The most common mole-based concentration unit
  • Symbolized M
  • Defined as the number of moles of solute per liter of solution
• In a dilution, the number of moles of solute does not change, only fewer per unit volume
• Dilution Equation

  • Knowing any three terms permits calculation of the fourth
  • M1 = molarity of solution before dilution
  • M2 = molarity of solution after dilution
  • V1 = volume of solution before dilution
  • V2 = volume of solution after dilution
• Water is often referred to as the "universal solvent"
• Water is an excellent solvent for polar molecules
• Water is the most abundant liquid on earth
• 60% of the human body is water
• Water transports ions, nutrients, and waste into and out of cells
• Water is the solvent for biochemical reactions in cells and digestive tract
• Water is a reactant or product in some biochemical processes
• Moles per liter (molarity)

  Molarity emphasizes the number of individual ions
• Equivalents per liter (eq/L)

  Emphasis on charge
• Equivalents

  1 M Na3PO4 - What is the concentration of ions? 1 M

  What is the concentration of ions? 3 M

  Equivalent is defined by the charge
• Equivalents/Liter

  The eq/mol value of the ion is simply the number of charges on the ion, regardless of whether that charge is positive or negative
• Active Transport

  Used in transporting and ions across the cell membrane

  Cellular energy must be expended to make concentration of ions different on each side of the cell membrane

  This is accomplished via large protein molecules embedded in cell membranes
• Na+ raised to the plus power and K+ raised to the plus power

  Danger to the body occurs when both in blood and in cells become too high or low
• The two most important anions in the body fluids are

  • Cl- raised to the minus power and HCO3- raised to the minus power
• A variety of proteins are also found as a colloidal dispersion in the blood
• Blood also transports nutrients and waste products