Ch 17 Rate of Reaction

• how can change in mass be used to measure rate of reaction?


  as reactants get used up -> their mass decreases

  as products get formed -> their mass increases

  (negative graph -> decrease in mass of reactants,

  positive graph -> increase in mass of products)

  (the faster the rate of reaction, the steeper the gradient)
• effective collisions

  when a chemical reaction occurs between particles
• we can measure rate of reaction in a given amount of time by observing

  how much product appears /

  how much reactant disappears
• how can volume of gas produced in the reaction be used to measure rate of reaction?


  observing production of the amount of gas in a given amount of time

  (the faster the rate of reaction, the steeper the gradient in graph)
• factors of rate of reaction


  concentration of reactants

  pressure of the system

  particle size of reactants

  temperature of the reaction mixture

  addition of a catalyst
• effect of concentration of rate of reaction


  concentration of reactants increases, number of reacting particles per unit volume increases

  they collide more frequently -> frequency of effective collisions also increases

  increase in rate of reaction
• effect of pressure on rate of reaction


  increase in pressure of gaseous reactants cause particles to be closer together

  they collide more frequently -> increases frequency of effective collisions

  increases rate of reaction

  effect of pressure on rate of reaction for liquid, solid reactants insignificant
• effect of particle size on rate of reaction

  decrease in particle size causes increase in surface area of solid reactants

  which allows more effective collisions

  increases rate of reaction
• data logger used when reaction is too vigorous for data to be collected manually

  measures changes in mass, temperature, pressure
• effect of temperature on rate of reaction

  higher temperatures -> reactant particles have more kinetic energy -> move and vibrate faster, which increases frequency of effective collisions

  higher temperatures -> more reactant particles possess energy greater than or equal to activation energy, which increases frequency of effective collisons

  increases rate of reaction
• catalyst


  increases the rate of chemical reactions without being chemically changed at the end of the reaction
• effect of catalyst on rate of reaction


  provide an alternative pathway of lower activation energy for the reaction to occur

  increases rate of reaction