Review the following concepts if needed - Thermochemistry Study Guide
Practice Problems
| 1. | Calculate the energy released when a 4,570 g piece of hot iron cools from 1000° C to 20° C. |
| 2. | Calculate the energy needed to heat 60 g of aluminum from 100° C to 250° C. |
| 3. | Calculate the final temperature of 295 g of water, initially at 30.0° C, if 4,500 joules are added. |
Calculate the standard enthalpy of reaction for the following reactions (don't forget to balance the equations first!). Also, indicate whether the reaction is exothermic or endothermic.
| 4. | C2H6(g) + O2(g) → H2O(g) + CO2(g) (combustion of ethane) |
| 5. | H2O(l) + CO2(g) → C6H12O6(s) +O2(g) (photosynthesis) |
| 6. | SO2(g) + O2(g) → SO3(g) |
| 7. | Fe(s) + O2(g) → Fe2O3(s) (oxidation of iron) |
| 8.Calculate the enthalpy change for P4(s) + 6Cl2(g) → 4PCl3(l) given |
| P4(s) + 10Cl2(g) → 4PCl5(s) ΔH = –1774.0 kJ |
| PCl3(l) + Cl2(g) → PCl5(s) ΔH = –123.8 kJ |
| 9.Calculate the enthalpy change for 2B(s) + 3H2(g)→ B2H6(g), given |
| 4B(s) + 3O2(g) → 2B2O3(g) ΔH = –2546 kJ |
 |
| B2H6(g) + 3O2(g) → 2B2O3(g) + 3H2O (g) ΔH = – 2035 kJ |
| H2O(l) → H2O(g) ΔH = 44kJ |
Answers
| 1. | –2.02 * 106 J = –2020 kJ |
| 2. | 8,010 J = 8.01 kJ |
| 3. | 33.6° C |
| 4. | – 1,428 kJ, exothermic |
| 5. | 2,802 kJ, endothermic |
| 6. | –89 kJ, exothermic |
| 7. | v826 kJ, exothermic |
| 8. | –1,774.0 kJ |
| 9. | +36 kJ |
Excerpted From:
From Chemistry Success in 20 Mintues A Day. Copyright © 2005 by LearningExpress, LLC. All Rights Reserved.
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