Rates of reactions

• What does the rate of chemical reactions refer to?

  The speed with which the reactants get turned into products
• Why is it important to measure the rate of a chemical reaction?

  To understand how fast reactants are used up or products are formed
• What is an example of a slow chemical reaction?

  The rusting of iron
• What is an example of a fast chemical reaction?

  The explosion of fireworks
• How can we measure the rate of a reaction?

  By measuring how fast reactants are used up or how fast products are formed
• What is the equation for the rate of reaction based on reactants used?

  Rate of reaction = quantity of reactants used / time taken
• What is the equation for the rate of reaction based on products formed?

  Rate of reaction = quantity of products formed / time taken
• What units can be used to measure quantities in the rate of reaction?

  Grams or cm³
• If 180 cm³ of hydrogen is produced in 2 minutes, what is the rate of reaction in cm³ per second?

  1. 5 cm³ per second
• If 3 g of magnesium takes 4 minutes to disappear completely, what is the rate of reaction in g per second?

  0.0125 g per second
• What do the rates of reactions calculated represent?

  The average or mean rates of reaction throughout the entire reaction
• How does the rate of reaction change over time?

  • Starts off fast when there are many reactants
  • Slows down as reactants are used up
• How can we visualize the rate of reaction on a graph?

  • Time on the x-axis
  • Mass of reactant remaining or volume of product produced on the y-axis
• What happens to the mass of magnesium in a reaction graph over time?

  The mass starts at 3 g and falls rapidly at first, then slows down
• What happens to the volume of hydrogen produced in a reaction graph over time?

  The volume starts at zero and quickly increases, then becomes less steep
• How would you calculate the rate of reaction in moles per minute if 0.6 moles of magnesium were used in 2 minutes?

  0.3 moles per minute
• What will be covered in the next video?

  • How to calculate the rate of reaction at a particular time
  • Difference from average rate throughout the entire reaction