Ch22 - Rates of reactions

• Catalyst - A substance that changes the rate of a chemical reaction without being used up. The catalyst will not be chemically unchanged.

  Rate of reaction - the change in concentration per unit divided by time taken.

  Average rate of reaction - volume of gas generated divided by time taken to produce the gas
• Factors affecting the rate of a reaction:

  • Types of reactants - magnesium vs. zinc in dilute HCl
  • Particle size - dilute HCl in small vs. large marble chips
  • Concentration - 0.5 molar HCl vs. 1.0 molar vs. 1.5 molar
  • Temperature - higher temp causes faster reaction
  • Catalysts - manganese dioxide in hydrogen peroxide
• Biochemical reaction - a reaction that occurs inside living cells. Ex)

  • Respiration - glucose goes through a reaction to release energy
  • Photosynthesis - CO2 and water react to form glucose in plants
  • Digestion - large food molecules break down into substances to be used by the body

  Biochemical reaction can be affected by:

  • Concentration of enzymes and substances where the enzyme is reacting, which is known as the substrate.
  • Temperature - many biochemical reactions occur at specific temperatures
  • pH - many enzymes only work in specific pH ranges