Chapter 15: Thermochemistry Campbell Chemistry Name: Date In Class Homework (due next class period)

Transcription

1 Date In Class Homework (due next class period) 2/15 Wednesday 2/16 Thursday 2/17 Friday 2/20 Monday 2/21 Tuesday 2/22 Wednesday 2/23 Thursday 2/24 Friday 2/27 Monday LSM 2/28 Tuesday 3/1 Wednesday Chapter 14 Test Calculations of Specific Heat and Heat in phase changes Equilibrium Lab NO SCHOOL Presidents Day In class notes: How to calculate Enthalpy (ΔH) Enthalpy and Entropy and Spontaneity Gibbs Free Energy in Class Notes Specific Heat Lab Finish Packet and Spontaneous or Not Spontaneous Review Chapter 15 Test Chapter 15: Video 1: Thermodynamics: Energy, Heat and Temperature Equilibrium Prelab OVER LONG WEEKEND: Chapter 15 Video 2: Thermochemistry: Enthalpy and Endo and Exothermic Reactions Chapter 15 Video 3: Entropy Specific Heat Prelab Study for Chapter 15 Test 1

2 Video 1. Energy, Heat and Temperature video: Textbook: Chapter 15 pages , 530 Guided Notes for Video on Heat and Temperature Define Energy Questions: What is Temperature? What is Heat? What is the unit of Heat (energy) What is the direction of heat flow? Define specific heat (c): Why does it take water longer to heat than most other materials (like sand)? (continued on next page) 2

3 What is calorimetry? What does each variable represent and its unit for this equation: Q = m c ΔT Q m c ΔT Show the work to solve the following problems: 5 g of copper was heated from 20 C to 80 C. How much heat was absorbed by the Cu? (c = 0.38 J/(g C)) If a 3.1 g ring is heated using 10.0 J, it s temp. rises by 17.9 C. Calculate the specific heat capacity of the ring. What are changes in state always accompanied by? What is the equation to calculate the heat required to change the state of a substance? Show the work for this practice problem: How much heat has to be removed to condense 25g of C 2H 5OH at its boiling point? H vap = 2260 J/g 3

4 Video 2. Thermochemistry: Enthalpy and Endo and Exothermic Reactions Textbook: Chapter 15 pages , Guided Notes for Video Enthalpy Questions: Define Thermochemistry Define Enthalpy How is an exothermic reaction different from an endothermic reaction What is the equation for calculating enthalpy change (ΔH) What are standard conditions for calculating enthalpy changes? Draw the energy graph of an exothermic reaction What happens to the temperature of the surroundings when a reaction is exothermic? (continued on next page) 4

5 What is the sign for ΔH when a reaction is exothermic (positive or negative)? Draw the energy graph of an endothermic reaction What happens to the temperature of the surroundings when a reaction is endothermic? What is the sign for ΔH when a reaction is endothermic (positive or negative)? Label the following reactions as exothermic or endothermic: 1. A + B AB ΔH = - 90 kj 2. A + C AC ΔH = kj 3. X + Y XY ΔH = + 2 kj 4. Z + X ZX ΔH = kj 5

6 In Class Notes on Calculating Enthalpy Changes: 1. What are the steps for calculating ΔH: 2. Calculate the ΔH for the following reaction: 2 NaOH (aq) + H 2SO 4(aq) Na 2SO 4(aq) + 2 H 2O (l) 3. Is this reaction exothermic or endothermic? 4. Calculate the ΔH for the following reaction: Ca(OH)2(c) + HCl(aq) CaCl2(aq) + H2O(l) 6

7 Video 3. Spontaneity and Entropy Textbook: Chapter 15 pages Guided Notes for Video on Entropy What is a spontaneous reaction? Questions: Define Entropy (S) What are the units: +ΔS means disorder which is -ΔS means disorder which is Rank solid, liquid, and gas for entropy (disorder). Why are gases the most disordered of all the states of matter? How does temperature affect Entropy? Predict ΔS for the following reaction: NH 4NO 3(s) N 2O (g) + 2 H 2O (l) 7

8 In Class Notes on Gibbs Free Energy: 1. What is Free Energy ΔG: 2. If ΔG is negative: 3. If ΔG is positive: 4. What is the equation to calculate ΔG? 5. What did I say about units? 6. Show the work for this practice problem: Calculate G at 298 K: 4 HCl (g) + O 2(g) --> 2 Cl 2(g) + 2 H 2O (g) ( H = kj, S = J/K) 7. What are favorable conditions for spontaneous reactions: 8. Fill out the following chart for spontaneous vs. nonspontaneous reactions: - G + G + S - S - H + H 8

9 In Class Work from Video 1: Heat of vaporization, heat of fusion, specific heat 1. How much heat in Joules is released if 11.8 g of water at 0 o C freezes to ice? 2. How much heat in Joules is absorbed if 1255 g of water at 100 o+ C boils to steam? Heat Capacity and Specific Heats of Water Joule Units specific heat of water 4.18 J/g o C specific heat of ice 2.06 J/g o C specific heat of steam J/g o C H f ice 334 J/g H v steam 2260 J/g 3. How much heat is required to warm 122 g of water from 10.0 o C to 33.0 o C? 4. As 55.6 g of a material cools from 50.0 o C to 35.2 o C, it loses 3080 J of heat. What is its specific heat? 5. What is the specific heat of a metal if the temperature of a 12.5 g sample increases from 19.5 o C to 33.6 o C when it absorbs 37.7 J of heat? 6. You have a sample of H 20 with mass 23.0 g at a temperature of C. How many joules of heat energy are necessary to: a. Heat the ice to 0 C b. Melt the ice? c. Heat the water from 0 C to 100 C? d. Boil the water? e. Heat the steam from 100 C to 109 C? 7. How many joules are needed to heat 40.0 g of copper from 13 C to 64 C? (specific heat of copper =.385 J/g o C) 8. What is the change in temperature if 25.0 g of copper absorbs 550 J of heat? (specific heat of copper =.385 J/g o C) 9

10 In Class Work for Video 2 and In class notes on calculating Enthalpy: Identify the followings reactions as exothermic and endothermic: Find H rxn for the following reactions. State whether they are endo or exothermic. Use the table on the back page of the packet. 9. 2KBr (s) + H 2 SO 4(l) K 2 SO 4(aq) + 2HBr (g) 10. Mg 3 N 2(s) + 6H 2 O (l) 3Mg(OH) 2(s) + 2NH 3(g) 11. NH 4 NO 3(s) N 2 O (g) + 2H 2 O (l) 12. 2NO (g) + O 2(g) 2NO 2(g) 13. 4Zn (s) + 9HNO 3(aq) 4Zn(NO 3 ) 2(aq) + NH 3(g) + 3H 2 O (l) 10

11 In Class Work for Video 3: Use the state symbols to determine whether the entropy increases or decreases, in addition determine the sign of S for the following reactions 14. Zn(NO 3 ) 2(aq) + 2NaOH (aq) Zn(OH) 2(s) + 2NaNO 3(aq) 15. 2NO 2(g) + H 2 O (g) HNO 2(aq) + HNO 3(aq) 16. Mg (s) + 2HNO 3(aq) Mg(NO 3 ) 2(aq) + H 2(g) 17. 4HBr (g) + O 2(g) 2H 2 O (l) + 2Br 2(l) In Class Work for Notes on calculating G Calculate G and predict the spontaneity of the following reactions at 298 K. 18. Sn (s) + 4HNO 3(aq) SnO 2(s) + 4NO 2(g) + 2H 2 O (l) ( H = -192 kj, S= 887 J/K) 19. 2N 2 O 5(g) 4NO 2(g) + O 2(g) ( H = 110 kj, S = 839 J/K) 20. Mn (s) + 2HCl (aq) MnCl 2(aq) + H 2(g) ( H = -221 kj, S = 79.7 J/K) 21. I 2(s) + Cl 2(g) 2ICl (l) ( H = kj, S = J/K) 22. Na 2 O (s) + SiO 2(s) Na 2 SiO 3(s) ( H = -192 kj, S = J/K) Nomenclature What is the formula of: 1. lithium nitride 1. Na 2O 2. barium chlorite 2. SrCO 3 What is the name of: 3. iron (III) nitrite 3. Pb 3(PO 4) 2 4. hydrofluoric acid 4. H 2Se 5. triulfur hexabromide 5. C 4O 6. chloric acid 6. HC 2H 3O 2 7. heptaphosphorous decoxide 7. Si 5N 8 8. tin (IV) hydroxide 8. Cu 2SO 3 9. carbonic acid 9. HNO magnesium nitride 10. KI 11

12 Answers J 2. 2,836,000 J 3. 11,700 J J/g0C J/g0C 6. a J b J c J d. 52,000 J e. 418 J J C kj/mol endo kj/mol exo kj/mol exo kj/mol exo kj/mol exo 14. decreases, - S 15. decreases, - S 16. increases, S 17. decreases, - S ALL SPONTANEOUS kj/mol kj/mol kj/mol kj/mol kj/mol 1. Li 3N 2. Ba(ClO 2) 2 3. Fe(NO 2) 3 4. HF 5. S 3Br 6 6. HClO 3 7. P 7O Sn(OH) 4 9. H 2CO Mg 3N 2 1. sodium oxide 2.strontium carbonate 3. lead (II) phosphate 4. hydroselenic acid 5. tetracarbon monoxide 6. acetic acid 7. pentasilicon octanitride 8. copper (I) sulfite 9. nitric acid 10. potassium iodide Thermodynamic Table H kj/mol H kj/mol Cu(c) 0 Mg(NO 3) 2(aq) -875 Cu(NO 3) 2(aq) -350 Mg(OH) 2(c) -925 CuSO 4(aq) -844 N 2(g) 0 H 2(g) 0 NH 3(g) HBr(g) NH 4Cl(aq) -300 HCl(g) NH 4NO 2(c) -256 HCl(aq) -167 NH 4NO 3(c) -366 HI(g) 1.72 N 2O(g) 82.0 HNO 2(aq) -119 NO(g) 90.2 HNO 3(aq) -207 NO 2(g) 33.2 H 2O(l) -286 N 2O 5(g) 11.3 H 2SO 4(l) -814 NaCl(c) -411 I 2(c) 0 NaCl(aq) -407 ICl(l) NaNO 3(aq) -446 KBr(c) -392 NaOH(aq) -470 KCl(aq) -419 Na 2SO 4(aq) K 2SO 4(aq) O 2(g) 0 Mg(c) 0 Zn(c) 0 Mg 3N 2(c) -461 Zn(OH) 2(c) -642 Zn(NO 3) 2(aq)