1441test4 - 1441 Test 4: Chapters 8 and 9 McMurry/Fay

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1441 Test 4: Chapters 8 and 9 McMurry/Fay http://dipowell1.home.mindspring.com/ Chapter 8 (Thermochemistry) 1. If a reaction is endothermic, then the : (a) reaction liberates heat (b) enthalpy of the reactants is higher than the enthalpy of the products (c) reaction cannot occur (d) enthalpy difference between products and reactants ( H) is positive (e) temperature will increase if the reaction occurs in a calorimeter 2. Which of the following chemical equations correctly represents the reaction in which the standard molar heat of formation of CO 2 is liberated? (a) C(g) + O 2 (g) CO 2 (g) (b) 2CO(g) + O 2 (g) 2CO 2 (g) (c) C(s) + O 2 (g) CO 2 (g) (d) C(s) + 2O(g) CO 2 (g) 3. What is the enthalpy change for the following reaction at standard conditions? SO 2 (g) + 3 H 2 (g) H 2 S(g) + 2 H 2 O(l) H f SO 2 (g) = -71.0 kcal/mole , H f H 2 S(g) = -4.8 kcal/mole , H f H 2 O(l) = -68.3 kcal/mole. 4. Calculate the enthalpy change for the reaction: 2NaBr(s) + I 2 (s) 2NaI(s) + Br 2 (g) Use the following data: Na(s) + ½ Br 2 (l) NaBr(s) H = -86 kcal Na(s) + ½ I 2 (s) NaI(s) H = -68.8 kcal Br 2 (l) Br 2 (g) H = 7.4 kcal 5. Calculate the Enthalpy change for: 2B(s) + 3H 2 (g) B 2 H 6 (g) given: 2B(s) + 3/2 O 2 (g) B 2 O 3 (s) ∆H = -1273 kJ B 2 H 6 (g) + 3O 2 (g) B 2 O 3 (s) + 3H 2 O(g) ∆H = -2035 kJ H 2 (g) + 1/2 O 2 (g) H 2 O(l) ∆H = -286 kJ H 2 O(l) H 2 O(g) ∆H = 44 kJ 6. CH 4 + 4Cl 2 CCl 4 + 4HCl H rxn = -4.34 X 10 5 J Based on the above reaction, what would be the energy change is 32 g of CH 4 reacted with an excess of chlorine? Is the energy absorbed or released? 7. N 2 + 3H 2 2NH 3 H = -92.2 kJ What is E? (reaction is carried out at constant P and 40 atm. Also, V = -1.12L.) 8. A balloon is inflated to its full extent by heating the air inside it. In the final stages of this process, the volume of the balloon changes from 4.00 X 10 6 L to 4.5 X 10 6 L by the addition of 1.3 X 10 8 J of energy as heat. Assuming that the balloon expands against a constant pressure of 1.0 atm, calculate ∆E for the process. ( to convert between L.atm and J, use 1 L.atm = 101.3 J.)
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9. A 0.5269 g sample of octane (C 8 H 18 ) is burned in a bomb calorimeter with a known heat capacity of 11.3 kJ/ o C. The temperature increase in the calorimeter is 2.25 o C. How much heat was released? How much heat would be released if one mole of octane is combusted? ( this problem omitted in 2004) 10. A student mixed 50 ml of 1 M HCl and 50 ml of 1 M NaOH in a coffee-cup calorimeter. The solution temperature increases from 21 o C to 27.5 o C. Calculate the enthalpy change for the reaction assuming that the lost of heat by the calorimeter is negligible, the total volume is 100 ml, the density of the solution is 1.0 g/ml, and the specific heat of the solution is 4.18J/g-K. What is the enthalpy change per mole of HCl or NaOH? 11.
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This note was uploaded on 01/03/2011 for the course CHEM 1441 taught by Professor Tanizaki during the Spring '08 term at UT Arlington.

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1441test4 - 1441 Test 4: Chapters 8 and 9 McMurry/Fay

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