1. 1
   A student reacts magnesium ribbon with dilute hydrochloric acid in a conical flask connected to a gas syringe, and records the volume of hydrogen gas collected every 10 seconds for 60 seconds.

   (a)

   A student measures that 24 cm3 of gas is produced from a reaction in 60 seconds. Which equation should be used to calculate the mean rate of reaction?

   [1 mark]

   • ARate = amount of product formed / time
   • BRate = time / amount of product formed
   • CRate = amount of product formed x time
   • DRate = time - amount of product formed

   (b)

   Using the equation for mean rate of reaction, what is the mean rate over the 60 seconds if 24 cm3 of gas was collected in total?

   [1 mark]

   • A60 cm3/s
   • B4 cm3/s
   • C1440 cm3/s
   • D0.4 cm3/s

   (c)

   The student notices that more gas is produced in the first 10 seconds than in the last 10 seconds of the reaction. Explain what this tells the student about how the rate of reaction changes over time.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A second student investigates the reaction between marble chips (calcium carbonate) and dilute hydrochloric acid by placing the flask on a balance and recording the total mass of the flask and contents every 20 seconds, as carbon dioxide gas escapes.

   (a)

   A different student measures the mass of a flask containing marble chips and acid every 20 seconds, as carbon dioxide gas escapes. Which equation would correctly calculate the mean rate of this reaction?

   [1 mark]

   • ARate = amount of reactant used x time
   • BRate = amount of product formed / time
   • CRate = final mass / initial mass
   • DRate = time / final mass

   (b)

   The flask and contents had a mass of 150.0 g at the start and 148.8 g after 60 seconds. What mass of carbon dioxide was produced (and escaped) in this time?

   [1 mark]

   • A2.0 g
   • B0.8 g
   • C1.2 g
   • D148.8 g

   (c)

   Calculate the mean rate of reaction, in g/s, for the first 60 seconds of this experiment, showing your working.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A technician reacts an excess of zinc granules with dilute sulfuric acid in a flask connected to a gas syringe, and plots a graph of the volume of hydrogen gas produced against time for the full reaction, from start to finish.

   (a)

   A graph is plotted of the volume of gas produced (cm3) on the y-axis against time (s) on the x-axis for a reaction between zinc and dilute sulfuric acid. Describe the shape of this graph and explain what the shape shows about the rate of reaction as the experiment proceeds.

   [3 marks]

   (b)

   Explain how the technician could use this graph to find the rate of reaction at a specific point in time, for example 20 seconds into the reaction, rather than the mean rate over the whole reaction.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A laboratory manager is training new technicians on how to analyse rate of reaction data, using results from a calcium carbonate and hydrochloric acid experiment as well as results from a magnesium and sulfuric acid experiment run under different conditions.

   (a)

   A student carries out an experiment reacting calcium carbonate with dilute hydrochloric acid and records the volume of carbon dioxide produced at regular time intervals from the start of the reaction until it stops. Describe how the student could calculate the mean rate of reaction over the whole experiment, and explain how the rate can be shown to change throughout the reaction using both a table of results and a graph.

   [6 marks]

   (b)

   The laboratory manager repeats the magnesium and sulfuric acid experiment twice: once with the acid at room temperature, and once with the acid heated to 40 degrees Celsius. Describe how the graphs of volume of hydrogen gas against time would differ between the two experiments, and explain what these differences show about the effect of temperature on rate of reaction, referring to how rate is calculated from such graphs.

   [6 marks]

   Total for question 4: 12 marks

End of questions