Name ____________________________________ Date ________ Period ____Chapter 17 Thermochemistry StudyGuide17.1 – 17.2 Thermochemical Equations1. Make the following conversions: a. 444 cal to joules b. 1.8 kJ to joules c. 0.45 kJ to calories2. Classify each of these processes as endothermic or exothermic: a. condensing steam c. evaporating alcohol b. burning alcohol d. baking a potato3. The specific heat capacity for silver is 0.24 J/goC. Calculate the energy required to raise the temperature of 150.0 g Ag from 273 K to 298 K. Calculate the molar heat capacity of silver.4. It takes 585 J of energy to raise the temperature of 125.6 g Hg from 20.0oC to 53.5oC. Calculate the specific heat capacity and the molar heat capacity of Hg.5. A 46.2-g sample of copper is heated to 95.4oC and then placed in a calorimeter containing 75.0 g water at 19.6oC. The equilibrium temperature in the calorimeter is 21.8oC. Calculate the specific heat capacity of copper; assuming that all the heat lost by the copper is gained by the water.6. A 15.0-g sample of nickel metal is heated to 100.0oC and dropped into 55.0 g of water, initially at 23.0oC. Assuming that all the heat lost by the nickel is absorbed by the water; calculate the final temperature of the nickel and the water. The specific heat of nickel is 0.444 J/goC.7. Haley was running bath water and realized it was too hot. If she has 20.0 L of water in the tub at 95oC and then adds 15.8 L of water at 75oC, what will the final temperature of the water be?8. For the combustion of methane, calculate the enthalpy change for the burning of 1.00 g of methane. CH4(g)+ 2O2(g) CO2(g) + 2H2O(l) + 890 kJ17.3 Heat in Changes of State9. Read heating curves (See Changes of State w/s) Label the phases, boiling point and melting point here: Indicate whether a heating curve would be flat or rising in 10-14. 10. liquid is boiling 13. PE is increasing 11. solid is warming 14. KE is increasing 12. solid is melting
17.3 Heat in Changes of State ProblemsValues for Water: (SHOW YOUR WORK FOR FULL CREDIT!!) Hfus = Hvap =CH2O(s) = 2.108 J/goC CH2O(l) = _______ J/goC CH2O(g) = 1.87 J/goC15. How much heat needs to be added to 10090 grams of ice at -10.0oC so that it all becomes a vapor at 120.0oC?16. If you are freezing special green ice cubes for St. Patrick’s Day, how much energy do you need to remove from 2 ice trays of 12 cubes if each cube holds 24.2 grams of water at 0oC?17. Trevor has a cold and wants to make steam in a vaporizer to help clear his congestion. How much energy will be required to change one gallon of liquid water at 100oC to steam at 100oC? (The density of water is 1.00g/ml)18. Rachel’s prom dress is all wrinkled, but she doesn’t have the time or patience to iron it. How much energy will be required to fire up the steamer to remove wrinkles if she adds 521 grams of water at 25.0oC and changes it all to steam at 100.oC?19. The steamer Andrew is using to strip the NASCAR wallpaper off his bedroom walls has used 32,967 kJ of energy. How many grams of water at 100 oC has he changed to steam at 100oC?20. Using a coffee cup calorimeter, Abby finds a balance that works and adds 1.60 g of NH4NO3 to 75.0 g of water at an initial temperature of 25.00oC. After the salt completely dissolves, the final temperature of the solution is 23.34oC. Assuming no heat is lost to the calorimeter; calculate the enthalpy change for the dissolution of NH4NO3 in kJ/mol.17.4 Hess’s Law and Standard Enthalpies of Formation21. Given the following data: H2(g) + ½ O2(g) → H2O(l) ΔH = -285.8 kJ N2O5(g) + H2O(l) → 2HNO3(l) ΔH = -76.6 kJ ½ N2(g) + 3/2 O2(g) + ½ H2(g) → HNO3(l) ΔH = -174.1 kJ Calculate the ΔH for the reaction 2N2(g) + 5O2(g) → 2N2O5(g)22. Use the values of ΔHof from the Appendix A handout to calculate the ΔHo for this reaction: SiCl4(l) + 2H2O(l) → SiO2(s) + 4HCl(aq)23. Use the values of ΔHof from the Appendix A handout to calculate the ΔHo for this reaction: (balance first!) NH3(g) + O2(g) → NO2(g) + H2O(l)VOCAB: (yes, you should be able to define these!!)calorie Heat heat of vaporizationendothermic heat capacity Jouleexothermic heat of fusion kinetic energy
molar heat capacity Specific heatpotential energy TemperatureANSWERS:1. Make the following conversions: a. 444 cal to joules = 1.86 x 103 J b. 1.8 kJ to joules = 1.8 x 103 J c. 0.45 kJ to calories = 1.1 x 102 cal2. Classify each of these processes as endothermic or exothermic: a. condensing steam – exo c. evaporating alcohol – endo b. burning alcohol – exo d. baking a potato – endo3. The specific heat capacity for silver is 0.24 J/goC. Calculate the energy required to raise the temperature of 150.0 g Ag from 273 K to 298 K. Calculate the molar heat capacity of silver.