Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Energetics
117 practice questions
Topics covered
- Exothermic reactions19 practice questions
- Endothermic reactions19 practice questions
- Measuring enthalpy changes of reactions19 practice questions
- Calorimetry experiments for determining the enthalpy changes of reactions18 practice questions
- Why do reactions either give out or absorb heat?19 practice questions
- Calculation of enthalpy changes of reaction using bond energies19 practice questions
Practice questions
21–30 of 51 · Easy
Question 21
3 marks · Easy
Answer and see the solution →A student performs a calorimetry experiment to investigate the reaction between calcium chloride and water. Their thermometer readings at one-minute intervals are shown in the table below:
Time (minutes) Temperature (°C) 0 21.0 1 23.1 2 24.8 3 24.5 4 24.1 (a)[1 mark]State the highest temperature recorded during the experiment.
(b)[1 mark]Calculate the temperature increase from 0 to the highest temperature.
(c)[1 mark]Suggest why the temperature decreases after 2 minutes.
Question 22
1 mark · Easy
Answer and see the solution →State the sign of the enthalpy change (ΔH) for an exothermic reaction.
Question 23
3 marks · Easy
Answer and see the solution →A student wants to measure the enthalpy change for the reaction: Describe three steps the student should take to ensure the experiment is as accurate as possible.
(a)[1 mark]Name one way to reduce heat loss during the experiment.
(b)[1 mark]State one way to improve the accuracy of temperature measurement.
(c)[1 mark]Give one way to ensure that the reaction mixture is uniform during the experiment.
Question 24
2 marks · Easy
Answer and see the solution →In a calorimetry experiment, a student mixes two solutions and records a 5.0 °C temperature rise. If 100 g of solution was used (specific heat capacity = 4.2 J/g°C), calculate the total heat energy released.
Question 25
1 mark · Easy
Answer and see the solution →State the main purpose of using a polystyrene cup in a calorimetry experiment to measure the enthalpy change of a reaction between two solutions.
Question 26
3 marks · Easy
Answer and see the solution →A student heats 80 g of water in a beaker using a chemical reaction. The temperature of the water rises from 20.2°C to 29.7°C. The specific heat capacity of water is 4.18 J/g°C.
(a)[1 mark]State the equation used to calculate the heat energy change (Q).
(b)[1 mark]Calculate the temperature change (ΔT) for this experiment. Show your working.
(c)[1 mark]Using your answer to (b), calculate the heat energy gained by the water (Q). Include the unit in your answer.
Question 27
2 marks · Easy
Answer and see the solution →In a calorimetry experiment, 2.60 g of potassium nitrate is dissolved in 65 g of water. The temperature of the water falls by 4.2°C. Calculate the molar enthalpy change (ΔH) for this process. The specific heat capacity of water is 4.18 J/g°C and the relative formula mass (M_r) for potassium nitrate is 101. Show your working. Give your answer in kJ/mol.
Question 28
2 marks · Easy
Answer and see the solution →A student’s value for the enthalpy change of combustion of methanol is much less exothermic than the accepted value found in data books. Explain two possible sources of error or limitations in the student’s calorimetry experiment.
Question 29
1 mark · Easy
Answer and see the solution →Name the piece of apparatus commonly used as a container for solution reactions in simple calorimetry experiments.
Question 30
3 marks · Easy
Answer and see the solution →(a)[1 mark]A student adds 40 g of water to a beaker. The initial temperature of the water is 22.0°C. A chemical reaction causes the temperature to rise to 30.5°C.
Calculate the temperature change, ΔT, for the water.
(b)[2 marks]The specific heat capacity of water is 4.18 J/g°C. Using your answer to part (a), calculate the heat energy gained by the water, Q, in joules. Give your answer to 2 significant figures.