Chemistry T6: Rate of reactions

• Factors that affect the rate of chemical reactions include temperature, concentration, surface area, catalysts, and pressure.
• Describe the effect of a catalyst on the position of the equilibrium

  No effect but increase rate of it reaching equilibrium - speeds up both forward and backward reactions equally.
• Describe the effect of changing the temperature on the position of the equilibrium

  If the temperature is increased, the equilibrium position moves in the direction of the endothermic process.
• Describe the effect of changing the concentration of reactant and product on the position of the equilibrium


  Shifts to the side with less conc

  
  

  If the concentration of the reactants increase, equilibrium shifts to the right(products). Vice versa
• Describe Le Chatelier's Principle

  If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract change and restore the equilibrium.
• What is dynamic equilibrium?

  in a closed system where the forward and reverse reactions occur at the same rate (and the concentrations of reactants and products remain constant)
• What is an enzyme?

  biological catalyst
• How do catalysts affect the reaction profile?

  Will lower the activation energy of the curve
• What is a catalyst and how does it work?

  A catalyst changes the rate of reaction but is not used up. It increases rate of reaction by providing a different pathway for the reaction that has a lower activation energy.
• Describe and explain the effect of increasing surface area

  smaller pieces= more sides exposed= greater surface area=increases frequency of collisions=more chance of successful collisions
• Describe and explain the effect of increasing pressure of a gas on the rate of reaction

  increasing the pressure of gas= increases number of gas molecules in same volume = increases the frequency of collision= more successful collisions = faster rate of reaction
• Describe and explain the effect of increasing concentration on the rate of reaction

  More particles = more frequent collisions = more successful collisions
• Describe and explain the effect of increasing temperature on the rate of reaction

  As T increases, kinetic energy of particles increases

  they move faster

  collide more frequently

  more chance of successful collisions
• What is the collision theory?

  Chemical reactions can occur only when reacting particles collide with each other and with activation energy
• What are the five factors affecting the rate of reaction?

  - Concentration of reactants

  - Pressure of gases (volume)

  - Surface area

  - Temperature

  - Catalysts
• Describe measuring the rate of reaction by monitoring the volume of a gas

  Connect a gas syringe to a reaction flask

  measure the volume of a gas formed in time intervals.

  Plot a graph of volume vs time.
• Describe measuring the rate by monitoring mass loss

  Place the reaction flask on a balance. In these reactions a gas is given off, so record the decrease in mass in time intervals (note hydrogen is too light). Plot a graph of mass vs time.
• Describe measuring the rate of reaction by monitoring the disappearance of a cross

  Take a piece of paper and mark a cross (X) on it. Put the reaction flask on this cross. Mix the reagents, and measure how long it takes for a cloudy mixture to conceal a cross.
• Name three common ways of measuring rate of reaction

  - Loss in mass of reactants

  - Volume of gas produced

  - Time for a solution to become cloudy
• What are the various units for rate of reaction

  Can include g/s or cm3 /s or mol/s

  
  

  Generally, mass/time, volume/time, moles/time
• How do you calculate the rate of reaction?

  Amount of reactant used/time

  OR

  amount of product formed / time
• Describe how increasing the pressure affects the equilibrium?

  Increasing the pressure shifts the equilibrium to the side with less moles