Paper 3: Required practical 3 - Effect of temperature on rate of a reaction

Question 1

How can rate of reaction be measured?

Answer 1

• Initial rates method - iodine clock
• Continuous monitoring method - measuring the volume of gas released in a reaction over time

Question 2

What are some issues with the disappearing cross experiment?

Answer 2

• It is judged by eye and so can’t be reliable
• May be a delayed reaction time with the stopwatch
• Slow reaction at low temperatures
• May not be enough precipitation for the cross to disappear

Question 3

How could you analyse the data?

Answer 3

• For a graph of amount of precipitate against time, it would be a straight line
• Gradient - rate of reaction
• Compare rate for each temperature

Question 4

What are the control variables?

Answer 4

• Concentrations of reactants and products
• Volumes of reactants and products
• Use the same beaker and cross underneath
• Use the same person to decide when the cross has disappeared

Question 5

How can we keep a substance at a constant temperature?

Answer 5

Using a water bath