5.1. Enthalpy change, \(\Delta H\)
A subsection of Chemistry, 9701, through 5. Chemical energetics
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The energy cycle shown can be used, along with suitable data, to calculate the enthalpy change of hydration of Ca2+. Each arrow indicates a transformation, W, X, Y and Z. Each transformation consists of one or more steps. Ca2++ 2Cl –Ca+ Cl 2CaCl 2CaCl 2W X Y Z The following data and data from the Data Booklet should be used. electron affinity of Cl = –349 kJ mol–1 enthalpy change of atomisation of Ca= +193 kJ mol–1 enthalpy change of formation of CaCl 2= –795 kJ mol–1 enthalpy change of solution of CaCl 2= –83 kJ mol–1 enthalpy change of hydration of Cl –= –364 kJ mol–1 Calculate the value of the enthalpy change corresponding to transformation W. Show your working.  enthalpy change W = kJ mol–1 Use your answer to and other data to calculate the value of the enthalpy change corresponding to transformation Z.  enthalpy change Z = kJ mol–1 Use your answer to to calculate the enthalpy change of hydration of Ca2+.  enthalpy change of hydration of Ca2+= kJ mol–1 Write an expression, in terms of W, X, Y and/or Z, to show how the enthalpy changes of two of the transformations can be used to calculate the lattice energy of CaCl 2. lattice energy of CaCl 2= State whether the lattice energy of CaCl 2is more or less exothermic than the lattice energy of MgF2. Explain your answer. The sulfates of the Group2 elements vary in solubility down Group2. Give the names of two solutions that could be mixed to form bariumsulfate. State and explain how the solubilities of the sulfates of the Group2 elements vary down Group2. 
9701_w20_qp_42
THEORY
2020
Paper 4, Variant 2
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In order to determine the enthalpy of neutralisation of a strong acid and a strong alkali, 25.0 cm3 of 2.00 mol dm‒3 sodium hydroxide is added to 25.0 cm3 of 2.00 mol dm‒3 hydrochloric acid. The increase in temperature is 12 C. In a second experiment, the same method is used, but 50.0 cm3 of 2.00 mol dm‒3 sodium hydroxide is added to 50.0 cm3 of 2.00 mol dm‒3 hydrochloric acid. What is the increase in temperature in the second experiment?
9701_w21_qp_11
MCQ
2021
Paper 1, Variant 1
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Questions Discovered
305