5. Chemical energetics
A section of Chemistry, 9701
Listing 10 of 306 questions
Define the term lattice energy. Use the following data to calculate a value for the enthalpy change of solution of copper(chloride, CuCl 2. You might find it helpful to construct an energy cycle. enthalpy change of hydration of Cl – = –378 kJ mol–1 enthalpy change of hydration of Cu2+ = –2099 kJ mol–1 lattice energy of CuCl 2= –2824 kJ mol–1  enthalpy change of solution of CuCl 2= kJ mol–1 The enthalpy change of hydration of Ca2+ is –1579 kJ mol–1. Use the Data Booklet to suggest why there is a big difference in the values of ∆Hhyd for Ca2+ and Cu2+. Identify the substances formed at the anode and at the cathode during the electrolysis of saturated CaCl 2. at the anode at the cathode  Calcium can be produced by the electrolysis of molten calciumchloride, CaCl 2. Calculate the mass, in g, of Ca formed when a current of 0.75 A passes through CaCl 2for 60minutes. [Ar: Ca, 40.1]  mass of Ca = g Explain what is meant by the term entropy of a system. Place one tick ( ) in each row of the table to show the sign of each entropy change, ∆S. process ∆S is negative ∆S is zero ∆S is positive NaCl dissolving in water water solidifying to ice  The evaporation of one mole of water has a standard Gibbs free energy change, ∆G o, of +8.6 kJ at 25 °C. Sketch a graph on the axes to show how ∆G o changes for this process between 25 °C and 150 °C at 101 kPa. positive negative 100 125 150 G o temperature / C  The reaction between A and B is feasible at low temperatures but is not feasible at high temperatures. A + B C + D Deduce the signs of ∆H and ∆S for this reaction and explain why the feasibility changes with temperature. sign of ∆H = sign of ∆S = 
9701_s21_qp_42
THEORY
2021
Paper 4, Variant 2
View
Questions Discovered
306