Transcript Bell Ringer
Bell Ringer 2NO(g) + O2(g) 2NO2(g) DH = -27 kcal Which graph represents the reaction shown above? A B Energy Energy Reaction Progress C Reaction Progress D Energy Energy Reaction Progress Reaction Progress Source: 2004 VA Chemistry EOC Exam Homework Answers 1. A, B 11. Amorphous 2. B 12. Higher 3. C 13. Dipole-dipole 4. B 14. Freezing 5. A 15. Hydrogen bonding 6. C 16. 30ºC 7. Inter 17. 1.0 atm 8. Intra 18. 40ºC 9. Dispersion forces 19. 47ºC 10. Boiling Point 20. 0.4 atm Practice with Enthalpy Calculate DH for the following reactions: 2 KBr (s) + I2 (g) 2 KI (s) + Br2 (l) DHtotal = [2mol (-327.9 kJ/mol) + 1mol (0 kJ/mol)] [2mol (-393.8 kJ/mol) + 1mol (0 kJ/mol)] DHtotal = 131.8 kJ 2 HCl (g) + 2 Ag ENDOTHERMIC 2 AgCl (s) + H2 (g) DHtotal = [2mol (-127.01 kJ/mol) + 1mol (0 kJ/mol)] [2mol (- 92.31kJ/mol) + 2mol (0 kJ/mol)] DHtotal = -69.40 kJ EXOTHERMIC Entropy and Gibb’s Free Energy They work the same way!! “PRODUCTS – REACTANTS” DStotal = DSproducts - DSreactants DS > 0, entropy increases (more disorder) DS < 0, entropy decreases (less disorder) DGtotal = DGproducts - DGreactants DG > 0, not spontaneous DG < 0, spontaneous DG = 0, equilibrium How do H, S, and G Relate? DG = DH - TDS Potassium bromide reacts with iodine at 345K. Will this reaction occur spontaneously? 2 KBr (s) + I2 (s) 2 KI (s) + Br2 (l) DHtotal = [2mol (-327.9 kJ/mol) + 1mol (0 kJ/mol)] [2mol (-393.8 kJ/mol) + 1mol (0 kJ/mol)] DHtotal = 131.8 kJ DStotal = [2mol (106.3 J/mol K) + 1mol (152.21 J/mol K)] [2mol(95.9 J/mol K) + 1mol (116.14 J/mol K)] DStotal = 56.87 J/ K How do H, S, and G Relate? DG = DH - TDS Potassium bromide reacts with iodine at 345K. Will this reaction occur spontaneously? 2 KBr (s) + I2 (s) DHtotal = 131.8 kJ x 2 KI (s) + Br2 (l) 1000 J = 131,800 J 1 kJ DStotal = 56.87 J/ K DG = 131,800 J – (345K)(56.87 J/K) DG = 131800 J – 19620.15 J DG = 112179.85 J 112,000 J = 112 kJ NOT SPONTANEOUS! Properties of Water Ms. Besal 3/24-27/2006 Characteristics of Water • Bent Shape H O • Hydrogen Bonding H • Liquid at Room Temperature • Requires great amount of energy to change (raise or lower) temperature • Expands as a solid • High boiling point • High surface tension • High heat of vaporization • “universal” solvent How does the flow of heat change water? DHvap = 40.7 kJ/mol 100ºC VAPORIZATION D CONDENSATION C LIQUID MELT 0ºC A B FREEZE DHfus = 6.02 kJ/mol SOLID TIME E GAS Phase Diagram of Water E B pressure FREEZE solid C liquid MELT CONDENSATION VAPORIZATION D . A gas SUBLIMATION DEPOSITION temperature Tc E B liquid pressure solid C D . A gas temperature A: Triple point – the temperature and pressure at which gas, liquid, and solid form of a substance all exist in equilibrium. B: Melting curve C: Vaporization curve D: Sublimation curve E: Critical point – the temperature and pressure above which gas cannot be liquefied no matter how much pressure is applied.