Name Date Block 1 Honors Chemistry Song Page 1

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1 Honors Chemistry Song Page 1 Test Unit 9 Thermodynamics Instructions: You may write your answers on the test, or on a separate piece of paper. Place your name or initials on each page you submit. Take the test with the class and complete it in the allotted time. When finished, please wait quietly for further instructions. Do these things and you may be awarded a bonus point. Bonus: Which is less, 1 cal or J? Submit your unit syllabus showing the assignments completed and scores recorded for a bonus point. Point values are denoted by square brackets []. Constants: c=3.00x10 8 m/sec h=6.63x10-34 Jsec Cp=1.00 cal/(g C) for water R=8.314 J/(mol K) = cal/(mol K) I. Selected Thermodynamic Data ΔH f, kj/mol, 25 C, 1 atm C6H12O6 (glucose) CO2 (g) H2O (g) H2O (l) CH C2H6(g) C3H8(g) C4H10(g) Al2O3(s) Fe2O3(s) II. Average Bond Energies (kj/mol) C-H 413 H-H 436 C-C 348 N-H 391 C-O 358 H-Cl 431 C=O 799 O-H 464 Cl-Cl 242 O=O 495 C=C 614 N-N 159 C C 839 N=N 418 N N 941

2 Honors Chemistry Song Page 2 III. Definitions 1. [5] Write the heat equation. Identify the variables. 2. [4] Write the enthalpy equation. Identify the variables. 3. [7] Write the equation for calculating heat of reaction using standard heats of formation. 4. [7] Write the equation for estimating heat of reaction using average bond energies. 5. [1] What is the standard heat of formation of the elements in their standard states? 6. [6] Complete the table: Is ΔH ΔH < 0 ΔH = 0 ΔH > 0 Is ΔH Endothermic, epidemic, or exothermic? Is ΔH a reactant or a product? What is the sign of ΔH? 7. [10] Describe the calorimetry experiment. How is the Law of Conservation of Energy applied to this experiment? Use an example from class in your answer.

3 Honors Chemistry Song Page 3 IV. Heating/Cooling Curves, Phase Diagram 1. [12] Draw the heating curve for dihydrogen monoxide. Clearly label all three phases, the phase changes, and the types of energy changes. 2. Consider the following phase diagram for methane, CH4. a. [5] Label the phases, the critical point, and the triple point b. [5] Describe what happens to the substance as I move it from point A to point B. Be sure to make note of the phase or phase change of the substance.

4 Honors Chemistry Song Page 4 V. Problems. Show your work. Mind units and sig figs. 1. Pretend that copper has a heat capacity of cal/(gc). a. [5] What is its heat capacity in units of J/(g C)? b. [5] What is its heat capacity in units of J/(mol C)? c. [5] How much heat must be added g of copper to raise its temperature 6.8 C? 2. Pretend that ΔHfus=80 cal/g for ice. a. [5] How much heat is needed to melt 25 g of ice b. [5] How much heat is needed to melt 10 moles of ice

5 Honors Chemistry Song Page 5 VI. Lab Problems. Show your work. Mind units and sig figs. 1. [10] Pretend we mix 50.0 g of 90 C water with g of 30 C water in an insulated vessel. Find the final temperature of the mixture. 2. Pretend that g of a copper colored metal, initially at C is added to g of 19.9 C water in an insulated vessel. The final temperature of the mixture is found to be 26.7 C. a. [10] Determine the heat capacity of the metal b. [5] Use Dulong and Petit s Law, Cp = 6.0 cal/(mol C) for nearly all metals, to identify the metal. 3. [10] Pretend that 25.0 g of ice at 0 C is added to g of 25.0 C water in an insulated vessel. After the ice is melted, what will be the final temperature of the mixture? Use ΔHfus=80 cal/g for ice.

6 Honors Chemistry Song Page 6 VII. Hess Law 1. Consider the reaction H2O(g) H2O(l) a. [5] Use standard heats of formation to compute the enthalpy of this phase change. b. [2] Is this an endothermic, or an exothermic process? Explain. 2. Consider methane a. [8] Write the balanced chemical equation for the combustion of methane (assume the water made is a gas). b. [10] Use standard heats of formation to calculate the heat of combustion of methane. c. [8] Draw Lewis structures for each reactant and product d. [10] Estimate the heat of combustion of methane gas using bond energies.

7 Honors Chemistry Song Page 7 3. Consider the following hypothetical reactions: A B A C ΔH = +60 kj ΔH = - 30 kj a. [3] Use Hess law to calculate the enthalpy change for the reaction B C b. [5] Construct the energy (enthalpy) diagram for substances A, B and C and show how Hess Law applies 4. [10] Use Hess Law to determine the heat of reaction for equation IV below. I: 2 O3 3 O2 ΔH = -427 kj II: O2 2 O ΔH = +495 kj III: NO + O NO2 ΔH = -233 KJ IV: NO + O3 NO2 + O2 ΔH =?

THE ENERGY OF THE UNIVERSE IS CONSTANT.

THE ENERGY OF THE UNIVERSE IS CONSTANT. Chapter 6 Thermochemistry.notebook Chapter 6: Thermochemistry Jan 29 1:37 PM 6.1 The Nature of Energy Thermodynamics: The study of energy and its interconversions Energy: the capacity to do work or to