Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
Endothermic reactions
19 practice questions
Practice questions
1–3 of 3 · Hard
Question 1
2 marks · Hard
Answer and see the solution →When 3.5 mol of substance X react with an acid, the reaction absorbs 96 kJ of heat energy from the surroundings.
Calculate the enthalpy change, , for this reaction in kJ/mol. State whether it is endothermic or exothermic.
Question 2
5 marks · Hard
Answer and see the solution →A student mixed 6.0 g of potassium nitrate (KNO₃, molar mass = 101 g/mol) in 50.0 g of water in a calorimeter. The temperature of the water fell by 3.2 °C. The specific heat capacity of water is 4.18 J g⁻¹ °C⁻¹.
(a)[2 marks]Calculate the number of moles of KNO₃ dissolved. (2 marks)
(b)[2 marks]Calculate the amount of heat (q, in J) absorbed by the water during the dissolving process. (2 marks)
(c)[1 mark]Calculate the enthalpy change, ΔH, for dissolving KNO₃ in kJ/mol. (1 mark)
Question 3
2 marks · Hard
Answer and see the solution →A reaction releases 212 kJ of heat when 7.0 mol of a reactant are completely used up. Calculate the enthalpy change, , in kJ/mol for this reaction. State the sign of and what it shows about the direction of energy transfer.