Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
Measuring enthalpy changes of reactions
19 practice questions
Practice questions
1–8 of 8 · Normal
Question 1
2 marks · Normal
Answer and see the solution →A student adds dilute hydrochloric acid to sodium hydroxide in a polystyrene cup. The temperature of the mixture rises.
State the name of this type of experimental method, and state the reason a polystyrene cup is used.
Question 2
4 marks · Normal
Answer and see the solution →A student investigates the enthalpy change when magnesium reacts with dilute sulfuric acid in a calorimeter.
(a)[1 mark]State the measurements the student should take during the experiment.
(b)[1 mark]Explain why it is important to stir the mixture before taking the final temperature reading.
(c)[1 mark]Suggest one reason the measured enthalpy change might be lower than the actual value.
(d)[1 mark]Describe how the student could improve the accuracy of this experiment.
Question 3
3 marks · Normal
Answer and see the solution →In a calorimetry experiment, 1.2 g of magnesium reacts with 100 cm³ of dilute hydrochloric acid. The temperature of the solution rises by 9.0 °C. Assume the specific heat capacity of water is 4.18 J/g°C and the density of the solution is 1.00 g/cm³.
Calculate the heat evolved in the reaction. Give your answer in kJ (kilojoules).
Question 4
3 marks · Normal
Answer and see the solution →When measuring the enthalpy change of a reaction between zinc and copper(II) sulfate solution in a calorimeter, a student notices bubbles forming.
Explain why bubbles might affect the temperature readings in this experiment. Suggest two ways the experiment could be improved to obtain more accurate results.
Question 5
4 marks · Normal
Answer and see the solution →A student measures the temperature change when potassium nitrate dissolves in water in a calorimeter. The data is shown below:
Time (min) Temperature (°C) 0 20.0 1 19.1 2 19.1 3 19.2 (a)[1 mark]Describe how the temperature of the solution changes during the experiment.
(b)[1 mark]Calculate the overall temperature change from 0 to 1 minute.
(c)[1 mark]What type of reaction is occurring? Explain using the data.
(d)[1 mark]Suggest why the temperature remains almost constant after 1 minute.
Question 6
1 mark · Normal
Answer and check →Which of the following changes would most improve the accuracy of a calorimetry experiment measuring enthalpy change?
- A.Using a glass beaker instead of a polystyrene cup
- B.Measuring the temperature change quickly after mixing
- C.Leaving the calorimeter uncovered during the reaction
- D.Using a wooden stirring rod to mix the solution
Question 7
2 marks · Normal
Answer and see the solution →Give two reasons why repeated trials are useful in calorimetry experiments.
Question 8
4 marks · Normal
Answer and see the solution →A student is investigating the enthalpy change for the reaction:
They use a polystyrene cup as a calorimeter.
(a)[2 marks]Draw a labelled diagram of the calorimeter setup.
(b)[2 marks]State two reasons why a polystyrene cup is used instead of a glass beaker.