A student carries out an investigation into the temperature change when a 5 cm length of coiled magnesium ribbon reacts with excess dilute sulfuric acid.
The student performs five experiments.
Experiment 1
• Rinse a burette first with distilled water and then with dilute sulfuric acid.
• Fill the burette with dilute sulfuric acid. Let some dilute sulfuric acid run out until the level is at the 0.0 cm^{3} mark.
• Use the burette to transfer 30.0 cm^{3} of dilute sulfuric acid into a boiling tube.
• Measure the starting temperature of the acid with a thermometer.
• Write down the starting temperature.
• Drop a coil of magnesium ribbon into the boiling tube. At the same moment, start a stop-watch.
• Stir the contents of the boiling tube continuously using the thermometer.
• After 1 minute, measure the temperature of the mixture in the boiling tube.
• Write down this temperature.
Experiment 2
• Refill the burette with dilute sulfuric acid. Let some dilute sulfuric acid run out until the level is at the 0.0 cm^{3} mark.
• Use the burette to transfer 25.0 cm^{3} of dilute sulfuric acid into a fresh boiling tube.
• Measure the starting temperature of the acid with the thermometer.
• Write down the starting temperature.
• Drop a coil of magnesium ribbon into the boiling tube. At the same moment, start the stop-watch.
• Stir the contents of the boiling tube continuously using the thermometer.
• After 1 minute, measure the temperature of the mixture in the boiling tube.
• Write down this temperature.
Experiment 3
• Repeat Experiment 2, but use 20.0 cm^{3} of dilute sulfuric acid instead of 25.0 cm^{3}.
Experiment 4
• Repeat Experiment 2, but use 15.0 cm^{3} of dilute sulfuric acid instead of 25.0 cm^{3}.
Experiment 5
• Repeat Experiment 2, but use 10.0 cm^{3} of dilute sulfuric acid instead of 25.0 cm^{3}.
(a)[4]
Complete Table 2.1 using the thermometer diagrams.
(b)[4]
Use Fig. 2.1 to complete a suitable y-axis scale and plot the results from Experiments 1 to 5. Then draw a line of best fit.
(c)[2]
Explain why the temperature increase varies as the volume of dilute sulfuric acid changes.
(d)[3]
Extend the line of best fit on your graph in Fig. 2.1 to work out the temperature increase if 33.0 cm^{3} of dilute sulfuric acid is used. Make it clear on Fig. 2.1 how you found your answer. temperature increase = ________
(e)[1]
On Fig. 2.1, sketch a line to represent the results you would expect. Label this line E.
(f(i))[1]
Give one reason why a burette, instead of a measuring cylinder, is used to measure the volume of the dilute sulfuric acid.
(f(ii))[1]
Explain why the contents of the boiling tube are stirred during each experiment.
(g)[2]
Describe one change to the apparatus that will give more accurate results. Explain your answer. change to apparatus ________ explanation ________
Worked solution & mark scheme
This 18-mark question has a full step-by-step worked solution and mark scheme. One marking point: “M1 all initial temperatures correct (21.0, 21.5, 21.5, 22.0, 22.0)” …