Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Physical Chemistry
442 practice questions
Topics covered
Practice questions
71–80 of 442
Question 71
2 marks · Normal
Answer and see the solution →State the two steps needed to calculate the molar enthalpy change (ΔH) from calorimetry data.
Question 72
4 marks · Normal
Answer and see the solution →Neutralisation experiments using polystyrene cups are often used to calculate enthalpy changes of reaction.
(a)[1 mark]Give one reason why a polystyrene cup is used instead of a metal can.
(b)[1 mark]Suggest one way the experiment might underestimate the enthalpy change.
(c)[1 mark]State one possible way to minimise errors from heat lost during the experiment.
(d)[1 mark]Explain how using a lid can help improve the accuracy of a calorimetry result.
Question 73
2 marks · Hard
Answer and see the solution →A student carries out a simple calorimetry experiment to measure the enthalpy change of combustion of a fuel. State two specific sources of error or limitations in this type of calorimetry experiment that could cause the measured value to be less exothermic (less negative) than the accepted value.
Question 74
5 marks · Hard
Answer and see the solution →Describe how you would carry out a calorimetry experiment to determine the enthalpy change of a displacement reaction between magnesium and copper(II) sulfate solution in a school laboratory. Your answer should refer to apparatus, measurements, and how you would ensure reliable results.
(a)[1 mark]State the main pieces of apparatus you would use for this experiment.
(b)[2 marks]Describe the basic procedure for mixing the reactants and measuring the temperature change.
(c)[2 marks]Suggest two ways to improve the reliability or accuracy of the results in this experiment.
Question 75
2 marks · Hard
Answer and see the solution →A student adds 25.0 g of water at 22.0 °C to a beaker. After a reaction occurs, the final temperature of the water is 29.5 °C. The specific heat capacity of water is 4.18 J/g°C. Calculate the amount of heat absorbed by the water during the reaction. Give your answer in joules.
Question 76
1 mark · Easy
Answer and see the solution →State what happens to energy when chemical bonds are formed.
Question 77
3 marks · Easy
Answer and see the solution →Methane reacts with oxygen as shown:
(a)[1 mark]State one bond broken in the reactants.
(b)[1 mark]State one bond formed in the products.
(c)[1 mark]Explain, using bond breaking and making, why this reaction releases heat.
Question 78
2 marks · Easy
Answer and see the solution →The equation below shows a reaction:
Bond Bond energy (kJ/mol) H–H 436 I–I 151 H–I 299 Calculate the overall enthalpy change (ΔH) for the reaction. State if it is exothermic or endothermic.
Question 79
2 marks · Easy
Answer and see the solution →Explain, in terms of bond breaking and bond making, why heating calcium carbonate is endothermic.
Question 80
3 marks · Easy
Answer and see the solution →The table shows average bond energies for some bonds:
Bond Bond energy (kJ/mol) C–C 348 C–O 358 O=O 498 Ethanol (C2H5OH) can be combusted in oxygen to form carbon dioxide and water. Use the data to answer the following:
(a)[1 mark]State which bond in the table requires the most energy to break.
(b)[1 mark]Complete the sentence: The combustion of ethanol is exothermic because the total energy released from making bonds is ____ than the energy needed to break bonds.
(c)[1 mark]Explain what the term 'average bond energy' means.