RI Energetics Remedial

Name: ………………………………………. ( ) Class: ……………. Date: ……………. Raffles Institution Year 5 H2 Chemistry 2024 ChemFocus T3W6 – Energetics Part 1 Notes: ⎯ Pre-ChemFocus Activity ⎯ • Familiarise yourself with the definitions of all enthalpies by reading through Pages 7 – 17 of your notes. • Watch the online Info-pack video IVY > C2025 – H2 CHEMISTRY > Pages > [ChemFocus] T3W6 Energetics > First video only • • •

Self-Check Questions 1. Complete the following table. Enthalpy change Equations Hcombustion (CH4(g)) CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) Hcombustion (C(s)) Hformation (CO2(g)) Hatomisation (Na(s)) Hhydration (Na+(g)) Hsolution (NaCl(s)) Hformation (NaCl(s)) Lattice energy of NaCl(s) 1st ionisation energy of Na 1st electron affinity of Cl Bond energy of Cl−Cl Hatomisation (Cl2(g)) Hatomisation (CH4(g)) 2. When 30 cm3 of 1.0 mol dm–3 CH3NH2, is added to 25 cm 3 of 1.0 mol dm–3 hydrochloric acid in a beaker, the temperature rose by 5.2 °C. The process efficiency is 90%. Calculate the standard enthalpy change of the reaction, assuming the specific heat capacity of water to be 4.18 J K–1 g–1. [2] Check your answers at IVY > C2025 – H2 CHEMISTRY > Pages > [ChemFocus] T3W6 Energetics > Remaining videos

3. Use the following data to c alculate the standard enthalpy change of solution of ammonium chloride. Lattice energy of ammonium chloride –705 kJ mol–1 Enthalpy change of hydration of NH4+ –307 kJ mol–1 Enthalpy change of hydration of Cl– –381 kJ mol–1 4. Use the following data to construct an energy cycle and hence calculate the enthalpy change for the hydrogenation of ethene gas, CH2=CH2(g), to ethane gas, CH3CH3(g). CH2=CH2(g) + H2(g) ⎯→ CH3CH3(g) Enthalpy change of combustion of CH3CH3(g) –1560 kJ mol–1 Enthalpy change of combustion of H2(g) –286 kJ mol–1 Enthalpy change of combustion of CH2=CH2(g) –1411 kJ mol–1

Tutorial Discussion Questions (to complete before Chemfocus session) 1a A student carried out an experiment to determine the enthalpy change of combustion of ethanol, CH3CH2OH, using the apparatus shown in the diagram. The results that the student obtained are shown in the table below. Mass of water / g 100 Initial temperature of water / °C 25.0 Final temperature of water / oC 31.5 Initial mass of burner and ethanol / g 62.57 Final mass of burner and ethanol / g 62.46 (i) Using the above experimental results, determine the experimental enthalpy change of combustion for ethanol. [3] (ii) Use the data below to calculate the standard enthalpy change of combustion of ethanol. [2] compound C2H5OH(l) CO2(g) H2O(l) Hf / kJ mol−1 –277.7 –394 –286 (iii) Suggest two rea