Unit 9 Thermodynamics

Name:____________________ Per:______ Unit 9 Outline- Thermodynamics, Reaction Rates, & Chemical Equilibrium Chapters 17 & 18 Vocabulary Condensation Freezing Vaporization Melting Boiling Sublimation Study Guide Deposition Heat Temperature Thermochemistry Exothermic Endothermic Calorimeter Joule Specific heat q= m ●c ● Δ T q= m Δ H vaporization q= m Δ H fusion Heat of reaction Le Chatlier’s principle Equilibrium Activation Energy Catalyst (Use notes, worksheets, and labs in addition to this study guide) 1. According to the collision theory, what 3 things must happen in order for two molecules to react? 2. What is the importance of the activation energy in a chemical reaction? 3. Using the collision theory, explain if the following would increase/ decrease the rate of reaction: a. Increase temp: 2 HCl(aq) + Mg(s)  MgCl2(aq) + H2(g) b. Increase HCl c. Increase pressure d. Remove MgCl2 4. Identify the following terms with their correct number/letter from the graphs: * Reactants* Products* Activation energy (number/letter & amount in Joules)* Is this reaction exothermic or endothermic? 5. Explain how a catalyst affects the activation energy in a chemical reaction. (Also, show on the above graph what a catalyst might do). e. Add H2 6. Explain what is wrong with the following statement: “When chemical equilibrium exists, the concentration of the reactants and products remain constant and the forward and reverse reactions cease.” 7. According to Le Chatelier’s principle, how does a system at equilibrium respond to stress? 8. Use the Le Chatelier’s principle to predict how the system at equilibrium would shift to relieve stress: I. CO (g) + 3 H2 (g)   CH4 (g) + H2O (g) + 113 J Stresses: a. adding CO b. Removing water c. Adding pressure d. Adding heat II. H2O(l) + heat <--> H2O(g) Stresses: a. add pressure b. remove heat c. add H2O(l) 9. Determine if the process is endothermic or exothermic in each of the following & why: a) hot pack (pack’s point of view) b) cold pack (pack’s point of view) c) H2 + O2  H2O + 483.6 kJ (heat) 10. Label: a) the phase change names c) endothermic or exothermic H 2O (Solid) d) H2O + 483.6 kJ (heat)  H2 + O2 b) temperatures at which the phase Δ occurs d) Amount of heat required for each phase change H 2O (Liquid) H 2O (Gas) 11. a) What does temperature measure? b) Why can we use °C in this unit (vs. K)? 12. a) What does heat measure? b) How is heat calculated & with what units? 13. What are the 2 different things an object can do with heat energy when it’s absorbed? 14. How can there be heat added/ removed during a phase change, yet there is no change in temperature? 15. Water has a very high specific heat. What does that tell you about water? 16. You are going to build a slide at a playground and your two option for materials are : Aluminum (specific heat = 0.897 J/ g º C) or Iron (specific heat 0.449 J/ g º C). Based on their specific heat, which would you chose & why? 17. Identify all the variables in the following equations & when you would use each equation: a. q= m ●c ● Δ T b. q= m Δ H vaporization c. q= m Δ H fusion 18. Ammonia (∆ H Vap = 1371 J/g) & alcohol (∆ H Vap for alcohol = 841 J/g) are left out in an open container. Which of these liquids would turn into a gas faster? Why? 19. If it takes 41.72 joules to heat a piece of gold weighing 18.69 g from 10 °C to 27 °C, what is the specific heat of gold? 20. How many joules of heat are needed to change 30.0 grams of steam at 105 °C down to a liquid at 45 °C? Make a graph to indicate this change.