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THERMOCHEMISTRY REVIEW

THERMOCHEMISTRY REVIEW. You need a marker board, marker, eraser, & your Chemistry book. What is the difference between kinetic and potential energy?. Potential energy is stored energy (as in chemical bonds) Kinetic energy is the energy of motion (as in the motion of molecules).

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THERMOCHEMISTRY REVIEW

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  1. THERMOCHEMISTRY REVIEW You need a marker board, marker, eraser, & your Chemistry book.

  2. What is the difference between kinetic and potential energy? • Potential energy is stored energy (as in chemical bonds) • Kinetic energy is the energy of motion (as in the motion of molecules)

  3. What is the difference between temperature and heat. • Heat is the total energy stored • Temperature is the average kinetic energy of the molecules

  4. Write the mathematical relationship between joules and calories. • 1 calorie = 4.18 joules Write the mathematical relationship between calories and kilocalories. 1000 calories = 1 kilocalorie

  5. A banana has 110. nutritional calories. How many joules of energy are in the banana? • 4.60 x 105 joules

  6. Endothermic reactions have ___________ H valuesand exothermic reactions have ___________ H values • Positive • Negative

  7. In an endothermic reaction the (system/surroundings) loses energy and the (system/surroundings) gains energy • Surroundings • System

  8. Ice Freezing Dry Ice Subliming Burning Marshmallow Sweat Evaporating Exothermic Endothermic Exothermic Endothermic Endothermic or Exothermic

  9. What is meant by specific heat? • The amount of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius

  10. Describe a calorimeter. What is it used for? • A calorimeter is an insulated device, such as a Styrofoam cup, used to measure the amount of heat absorbed or released during a chemical reaction.

  11. Use the table of specific heat values on page 492 of your text to answer the following question.The temperature of a sample of iron with a mass of 15.0 g changed from 25.5°C to 85.6°C. How many kilojoules of energy did this process take? • q = (15.0)(0.449)(60.1) = 405 J = 0.405 kJ

  12. Draw a heating curve for ammonia as it is warmed from -120°C to 300°C. The freezing point of ammonia is -108°C and its boiling point is 270°C.

  13. If 0.345 kJ of heat is released by 125 g water as it cools down from 85.2°C, what is it’s new temperature? • 85.86ºC

  14. If the heat of fusion for ammonia is 5.66 kJ/mol, how many kJ would be required to melt 22.6 g of ammonia? • 7.51 kJ

  15. Using the following thermochemical equation: 2CO(g) + O2(g)  2CO2(g) ΔH = -566.0 kJ, answer the following questions. a. If 2.45 g of CO(g) reacts with sufficient oxygen gas, how many kJ of heat are released? b. How many grams of carbon dioxide were produced when 234 kJ of heat were made? • a. - 24.8 kJ • b. 36.4 g CO2

  16. Given the following data, determine the ΔH for the reaction: 2 Cu(s) + O2(g)  2 CuO(s)4CuO (s)  2Cu2O (s) + O2 (g) ΔH = 288kJCu2O (s)  Cu (s) + CuO (s) ΔH = 11kJ • -310 kJ (1st reaction flipped, 2nd flipped and doubled)

  17. What is meant by the term “enthalpy?” • Enthalpy (H) is the heat content of a system at a constant pressure

  18. Explain how the Heat of Fusion and the Heat of Vaporization are the same and different.

  19. Which has more entropy, a sugar cube or a sugar solution? • Sugar Solution If a sugar cube dissolves in water, is the “S” for the reaction positive or negative? Positive

  20. Calculate the ΔG for this reaction at 298 K (room temperature ) and 1000K (very hot). Determine if each reaction is spontaneous. O2 + O  O3 ΔH = -106.5kJ ΔS = -127.4 J/K Answer: at 298K ΔG=-68.5kJ so the reaction is spontaneous at 1000K ΔG=20.9 kJ so the reaction is not spontaneous

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