C6

• How to find rate of reaction at a certain time in a graph of amount of reaction vs time?


  Slope of tangent at that time
• What is the formula for calculating the rate of reaction?


  Rate of reaction = amount of reactant used or product formed / time
• What is the higher tier formula for rate of reaction in moles?


  Rate of reaction (mol/s) = Moles of reactant used or product formed / time
• What are the various units for rate of reaction?


  Units can include g/s, cm^3/s, or mol/s
• Name three common ways of measuring the rate of reaction.


  • Loss in mass of reactants
  • Volume of gas produced
  • Time for a solution to become opaque
• How is the rate of reaction measured by monitoring mass loss?


  • Place the reaction flask on a scale.
  • Record the decrease in mass in time intervals.
  • Plot a graph of mass vs time.
• How is the rate of reaction measured by monitoring the volume of gas?


  • Connect a gas syringe to a reaction flask.
  • Measure the volume of gas formed in time intervals.
  • Plot a graph of volume vs time.
• How is the rate of reaction measured by monitoring the disappearance of a cross?


  • Mark a cross on a piece of paper.
  • Place the reaction flask on the cross.
  • Measure how long it takes for the cross to be concealed by a cloudy mixture.
• How do you find the rate of reaction at some time, t, from a graph of amount of reactant vs time?

  Find the tangent to the curve at time t; the gradient indicates the rate.
• State five factors affecting the rate of a chemical reaction.

  • Concentration of reactants
  • Pressure of gases
  • Surface area
  • Temperature
  • Catalysts
• What is the collision theory?


  Chemical reactions occur when reacting particles collide with sufficient energy.
• Describe the effect of increasing temperature on the rate of reaction.

  • Temperature increases = faster reaction.
  • Kinetic energy of particles increases.
  • More energetic collisions and more frequent collisions.
  • No direct proportionality between rate and temperature.
• Describe the effect of increasing concentration on the rate of reaction.


  • Concentration increases = faster reaction.
  • More reactants lead to more frequent collisions.
• Describe the effect of increasing pressure of a gas on the rate of reaction.


  • Increasing pressure increases the number of gas molecules in the same volume.
  • More frequent collisions lead to a faster reaction.
  • Increasing volume retards the reaction.
• Describe the effect of increasing surface area on the rate of reaction.


  • Smaller pieces of solid reactants have a greater surface area.
  • Increased surface area leads to more frequent collisions.
  • Example: magnesium powder reacts faster than a block of magnesium.
• What is a catalyst and how does it work?


  • A catalyst changes the rate of reaction but is not used up.
  • It provides a different pathway with lower activation energy.
  • The reaction profile has a lower maximum for catalyzed reactions.
• What is an enzyme?


  An enzyme is a molecule that acts as a catalyst in a biological system.
• What is a reversible reaction?


  A reversible reaction occurs when products can react backwards to form original reactants.
• When is dynamic equilibrium reached?


  Dynamic equilibrium is reached when forward and reverse reactions occur at the same rate in a closed system.
• Describe Le Chatelier’s Principle.


  If a system at equilibrium experiences a change, it responds to counteract that change and restore equilibrium.
• Describe the effect of changing the concentration of reactant and product on the position of the equilibrium.

  • Changing concentration disrupts equilibrium.
  • Increasing reactant concentration forms more products.
  • Decreasing product concentration leads to more reactants forming.
• Describe the effect of changing temperature on the position of the equilibrium.

  • Increasing temperature increases products for endothermic reactions.
  • Increasing temperature decreases products for exothermic reactions.
• Describe the effect of changing pressure on the position of the equilibrium.

  • Increase in pressure shifts equilibrium towards the side with fewer molecules.
  • Decrease in pressure shifts equilibrium towards the side with more molecules.
  • No effect if gas molecules are equal on both sides.
• Describe the effect of a catalyst on the position of the equilibrium.

  • A catalyst has no effect on the position of equilibrium.
  • It speeds up both forward and backward reactions equally.
  • Equilibrium is achieved faster.