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NOTE: After completing each session, check all task/PPQ answers using answers at the back. Page 4. 4. Session 1 - Recap of AS Energetics. 1 ...
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Session Title Work to be completed Resource provided Outcome On-Line Support 1 Recap of AS Energetics Read through content to recap AS Energetics and apply to related recap questions in task 1 Work pack IV Page(s) 3 – 8 Complete: Task 1 Session 1 Recap of AS Energetics (VLE) 2 Definitions Review the table of key definitions and use these to complete task 2. Work pack IV Page(s) 9 – 10 Textbook Page(s): 258 – 260 Complete: Task 2 3 MS Teams Lesson Wednesday Live lesson: Enthalpy of Solution Calculations Work pack IV Pages(s) 11 – 13 Textbook page(s): 267 – 268 Complete: 1 - DO NOW 2 - Checking for Understanding Question(s) 3 - Application Question(s) 4 Enthalpy of Solution Calculations Complete task 3 questions using information from previous session Work pack IV Pages(s) 14 Textbook page(s): 267 – 268 Complete: Task 3 Session 4 Enthalpy of Solution Calculations (VLE) 5 MS Teams Lesson Friday Live lesson: Born Haber Cycle Work pack IV Pages(s) 15 – 17 Textbook page(s): 261 – 266 Complete: 1 - DO NOW 2 - Checking for Understanding Question(s) 3 - Application Question(s) 6 Born Haber Cycle Calculations Complete task 4 questions using information from previous session Work pack IV Pages(s) 18 Textbook page(s): 261 – 266 Complete: Task 4 Session 6 Born- Haber Cycle Calculations (VLE) 7 Application of New Theory Complete a series of PPQs on the theory you have covered since session 2 Work pack IV Pages(s) 19 – 22 Complete: Past paper exam questions, Q. 1 to Q. 5 8 MS TEAMS Lesson Wednesday Live lesson: Comparing Experimental and Theoretical Enthalpy Values Work pack IV Pages(s) 23 - 24 Textbook page(s): 267 – 268 Complete: 1 - DO NOW 2 - Checking for Understanding Question(s) 3 - Application Question(s)
This is the enthalpy change for a reaction with the quantities shown in the chemical equation. This means that the value should always be quoted along with the equation. In this example, the second equation contains half the molar quantities of the first and so the (^) rH value is half as much. e.g. H 2 SO 4 (aq) + 2 NaOH(aq) → Na 2 SO 4 (aq) + 2 H 2 O(l) ΔrH° = – 114.2 kJ mol-^1 ½ H 2 SO 4 (aq) + NaOH(aq) → ½ Na 2 SO 4 (aq) + H 2 O(l) ΔrH° = – 57.1 kJ mol-^1 the value of – 114.2 kJ mol-^1 in the first equation means that 114.2 kJ of heat energy is released when 1 mole of H 2 SO 4 reacts with 2 moles of NaOH. the value of – 57.1 kJ mol-^1 in the second equation means that 57.1 kJ of heat energy is released when ½ mole of H 2 SO 4 reacts with 1 mole of NaOH.
Enthalpy change when 1 mole of a substance is formed from its constituent elements with all reactants and products in standard states under standard conditions. e.g. CH 4 (g) C(s) + 2 H 2 (g) → CH 4 (g) H 2 O(l) H 2 (g) + ½ O 2 (g) → H 2 O(l) NH 3 (g) ½ N2(g) + 3/2 H2(g) → NH3(g) C 2 H 5 OH(l) 2 C(s) + 3 H2(g) + ½ O2(g) → C2H5OH(l) CH 3 Br(l) C(s) + 3/2 H2(g) + ½ Br2(l) → CH3Br(l) Na 2 O(s) 2 Na(s) + ½ O2(g) → Na2O(s) Note: re ΔfHº of an element in its standard state = 0 by definition
Enthalpy change when 1 mole of a substance is completely burned in oxygen with all reactants and products in standard states under standard conditions. e.g. CH4(g) CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l) H2(g) H2(g) + ½ O2(g) → H2O(l) C2H6(g) C2H6(g) + 3½ O2(g) → 2 CO2(g) + 3 H2O(l) C2H5OH(l) C2H5OH(g) + 3 O2(g) → 2 CO2(g) + 3 H2O(l) Na(s) Na(s) + ¼ O2(g) → ½ Na2O(s) C6H14(l) C6H14(g) + 9½ O2(g) → 6 CO2(g) + 7 H2O(l)
definitions given in the table on the previous page. 1. ΔfH of C 6 H 6 (l) ………………………………………………………………...………………………….. 2. ΔfH of CH 3 COOH(l) ……………………………………………………………………………………... 3. ΔcH of H 2 (g) ……………………………………………………………………………………………… 4. ΔcH of CH 3 COOH(l) …………………………………………………………………………………….. 5. 1st ionisation energy of aluminium ……………………………………………………………….…… 6. 2nd ionisation energy of aluminium ………………………………………………………………...… 7. 3rd ionisation energy of aluminium …………………………………………………………………… 8. 1st electron affinity of chlorine ………………………………………………………………………… 9. lattice enthalpy of formation of sodium oxide ……………………………………………………...... 10. lattice enthalpy of dissociation of aluminium oxide ………………………………………………… 11. ΔhydH of sodium ions ………………………………………………………………………………….. 12. Enthalpy of vaporisation of bromine ………………………………………………………….......... 13. ΔsolH of sodium hydroxide …………………………………………..………...........................…… 14. Enthalpy of fusion of sodium chloride ………………………………………………...............…… 15. Bond dissociation enthalpy of water ……………………………………………….....................… 16. Bond dissociation enthalpy of hydrogen ………………………………………….......…………… 17. ΔatmH of bromine ………………………………………………………...................................…… 18. Bond dissociation enthalpy of bromine ……………………………………………………........… 19. 1st electron affinity of bromine …………………………………………………….................…… 20. 2nd electron affinity of sulphur ………………………………………………………….............…
With positive ions, there may only be loose ion-dipole attractions between the δ- oxygen atoms in the water molecules and the positive ions, or there may be formal dative covalent (co-ordinate covalent) bonds. With negative ions, ion-dipole attractions are formed between the negative ions and the δ+ hydrogens in water molecules. The size of the hydration enthalpy is governed by the amount of attraction between the ions and the water molecules.
So... ΔHsol = +2258 - 1650 + 2(-364) ΔHsol = - 120 kJ mol- 1 Whether an enthalpy of solution turns out to be negative or positive depends on the relative sizes of the lattice enthalpy and the hydration enthalpies. In this particular case, the negative hydration enthalpies more than made up for the positive lattice dissociation enthalpy.
The notes in this section will help supplement what you will cover in the MS Teams lesson and allow you to successfully complete the tasks in the sessions to follow.
Use this data in the questions that follow. kJmol-^1 Na K Ca Al Co Cu Br I O S Cl enthalpy of atomisation +107 +90 +193 +314 +427 +112 +107 +248 +279 + 1st ionisation enthalpy +496 +418 +590 +577 +757 + 2nd ionisation enthalpy +4562 +3070 +1150 +1820 +1640 + 3rd ionisation enthalpy +6910 +4600 +4940 +2740 +3230 + 1st electron affinity (^) – 342 – 142 – 200 – 364 2nd electron affinity +844 + 1 Calculate the enthalpy of formation of potassium chloride given that the lattice enthalpy of formation of potassium chloride is – 710 kJmol-^1. 2 Calculate the lattice enthalpy of formation of sodium sulfide given that the enthalpy of formation of sodium sulfide is – 370 kJmol-^1. 3 Calculate the enthalpy of formation of calcium bromide given that the lattice enthalpy of formation of calcium bromide is – 2125 kJmol-^1. 4 Calculate the lattice enthalpy of formation of aluminium oxide given that the enthalpy of formation of aluminium oxide is – 1669 kJmol-^1. 5 Calculate the first electron affinity of iodine given that the lattice enthalpy of dissociation of calcium iodide is +2054 kJmol-^1 and its enthalpy of formation is – 535 kJmol-^1. 6 Calculate the enthalpy of atomisation of copper given that the enthalpy of formation of CuO is – 155 kJmol-^1 and its lattice enthalpy of formation is – 4149 kJmol-^1. 7 The lattice enthalpy of formation of the three possible chlorides of cobalt are given: CoCl – 700; CoCl 2 – 2624; CoCl 3 – 5350 kJmol-^1. a) Using Born-Haber cycles, calculate the enthalpy of formation of each chloride. b) Which of these chlorides is energetically stable with respect to their elements under standard conditions? c) Which compound is likely to be formed when cobalt and chlorine react under normal conditions?
Q1. Which equation represents the process that occurs when the standard enthalpy of atomisation of iodine is measured? A I 2 (s) → I(g) B I 2 (s) → 2I(g) C I 2 (g) → I(g) D I 2 (g) → 2I(g) (Total 1 mark) Q2. This question is about magnesium chloride. (a) Write the equation, including state symbols, for the process corresponding to the enthalpy of solution of magnesium chloride.
(1) (b) Use these data to calculate the standard enthalpy of solution of magnesium chloride. Enthalpy of lattice dissociation of MgCl 2 = +2493 kJ mol–^1 Enthalpy of hydration of magnesium ions = – 1920 kJ mol–^1 Enthalpy of hydration of chloride ions = – 364 kJ mol–^1
(2) (c) Solubility is the measure of how much of a substance can be dissolved in water to make a saturated solution. A salt solution is saturated when an undissolved solid is in equilibrium with its aqueous ions. Use your answer to part (b) to deduce how the solubility of MgCl 2 changes as the temperature is increased. Explain your answer.
(3) (Total 6 marks) Q3. Thermodynamics can be used to investigate the changes that occur when substances such as calcium fluoride dissolve in water. (a) Give the meaning of each of the following terms. (i) enthalpy of lattice formation for calcium fluoride
(2)