Name_______________________________________________period________Chapter 5 worksheet 1. 2. 3. 4. 5. 6. 7. 8. 9. What is energy? The measure of the ability to do work What is heat? A form of energy that is transferred because of temperature differences What is the SI unit for heat? Joule What is an exothermic reaction? A reaction where energy is released What is an endothermic reaction? A reaction where energy is absorbed What is enthalpy? The heat content of a substance What is the sign of О”H for an exothermic reaction? negative What is the sign of О”H for an endothermic reaction? positive Consider the following reaction, which occurs at room temperature and pressure: 2Cl (g) пѓ Cl2 (g) О”H = -243.4 kJ Which has higher enthalpy under these conditions, 2Cl (g) or Cl2(g) 10. Consider the following reaction: 2Mg(s) + O2(g) пѓ 2MgO(s) О”H = -1204 kJ a. Is this reaction exothermic or endothermic? exothermic b. Calculate the amount of heat transferred when 2.4 g of Mg react 59 J released c. Will the surroundings get warmer or colder when the reaction proceeds? Warmer 11. How much heat is released when 15.0 g of copper with a specific heat capacity of 0.385 J g-1вЃ°C-1 is cooled from 80 вЃ°C to 35 вЃ°C? 260 J 12. If 500 J of heat are added to 100.g sample of each of the substances listed below, which will have the largest temperature increase? Gold specific heat = 0.129 J g-1K-1 Silver specific heat = 0.237 J g-1K-1 Copper specific heat = 0.385 J g-1K-1 Water specific heat = 4.18 J g-1K-1 13. If 100.0 J of heat are added to a 150.0 g sample of water at 25.0 вЃ°C, what is the final temperature of the water? 25.159 вЃ°C 14. What are more thermodynamically favored, exothermic or endothermic reactions? exothermic 15. Will exothermic reactions feel hot or cold? hot 16. Will endothermic reactions feel hot or cold? cold 17. The heat released from the combustion of 0.0500 g of white phosphorus increases the temperature of 150.0 g of water from 25.0 вЃ°C to 31.5 вЃ°C. Calculate the value of the enthalpy change in kJ mol-1 of the combustion of phosphorus. -4500 kJ mol-1 18. When a 6.50 g sample of solid sodium hydroxide dissolves in 100.0 g of water in a Styrofoam cup, the temperature rises from 21.6 вЃ°C to 37.8 вЃ°C. Calculate О”H (in kJ mol-1) for the solution process. -42.3 kJ mol-1 19. Consider the combustion of liquid methanol: CH3OH (l) + 3/2 O2(g) пѓ CO2 (g) + 2H2O (l) О”H = -726.5 kJ a. What is the enthalpy change for the reverse reaction? 726.5 kJ b. Balance the forward reaction with whole-number coefficients. What is О”H for the reaction represented by this equation? 2CH3OH (l) + 3 O2(g) пѓ 2CO2 (g) + 4H2O (l) О”H = -1453kJ c. Which is more likely to be thermodynamically favored the forward or reverse reaction? forward d. If the reaction were written to produce H2O (g) instead of H2O (l), would you expect the magnitude of О”H to increase, decrease, or stay the same? Explain. It takes energy to go from liquid water to gaseous water, so О”H would increase (less negative) 20. Given the following enthalpies of reaction: P4(s) + 3O2(g) пѓ P4O6 (s) О”H = -1640.1 P4(s) + 5O2(g) пѓ P4O10(s) О”H = -2940.1 Calculate the enthalpy change for P4O6(s) + 2O2(g) пѓ P4O10(s) -1300 kJ 21. Given the following enthalpies of reaction: H2(g) + F2(g) пѓ 2HF(g) О”H = -537kJ C(s) + 2F2(g) пѓ CF4(g) О”H= -680 kJ 2C(s) + 2H2(g) пѓ C2H4(g) О”H=52.3 kJ Calculate the enthalpy change for C2H4 (g) + 6F2(g) пѓ 2CF4(g) + 4HF(g) -338 kJ 22. What is meant by standard conditions with reference to enthalpy changes? Room temperature and all compounds/elements are in their standard states 23. Which of the following does not have a standard heat of formation value of zero at 25 вЃ°C and 1.00 atm? a. Cl2(g) b. I2 (s) c. Br2(g) d. Na(s) 24. Calculate the enthalpy change for the reactions a.Fe3O4 (s) + 2C(s) пѓ 3Fe(s) + 2CO2 (g) 906 kJ b.2NO2(g) пѓ N2O4 (g) -57.2 kJ c. 4FeO(s) + O2 (g) пѓ 2Fe2O3(s) -1100 kJ Given the following О”Hf Fe3O4 (s) -118 kJ mol-1 CO2 (g) -394 kJ mol-1 NO2(g) 33.2 kJ mol-1 N2O4 (g) 9.2 kJ mol-1 FeO(s) -271.9 kJ mol-1 Fe2O3(s) -822.16 mol-1 25. Is breaking bonds endothermic or exothermic? endothermic 26. Is forming bonds endothermic or exothermic? exothermic 27. Using bond energies from the data booklet, find the enthalpy change for the following reactions. a. C2H4 + H2 пѓ C2H6 -124 kJ b. 2H2 + O2 пѓ 2H2O -484 kJ Try the practice questions on pg. 113 Review: 1. The density of aluminum is 2.7 g/mL. What is the volume of 8.1 g? 3.0 L 2. Na, K, Li, and Cs all share similar chemical properties. In the periodic table, they most likely belong to the same a. Row b. period c. group d. element 3. An unknown element is shiny and a good conductor of electricity. What other properties would you predict for it? Malleable, ductile, high melting point/boiling points 4. Write the names of each element and identify them as a metal, nonmetal, metalloid, or noble gas a. K b. Si c. Hg d. Ag e. Na f. He Potassium silicon mercury silver sodium helium Metal metalloid metal metal metal noble gas 5. A certain ion has an atomic number of 16, a mass number of 33, and 18 electrons. a. What is the charge on the ion? -2 b. What is the identity of this ion? sulfur c. How many neutrons does the nucleus of this ion have? 17 6. What is the charge on a magnesium ion that has 10 electrons? +2 7. Find the mass for each of the following a. 6.75 mol lead b. 3.01 x 10 23 atoms of F 8. Find the number of atoms in each of the following (show work) a. 1.50 mol Na d. 0.025 kg aluminum 9. Find the number of moles in each of the following (show work) a. 0.11 kg Na d. 2.25 x 10 25 atoms Zn 10. For each group, tell if the atoms will gain or lose electrons to become ions and tell how many electrons are involved. a. Group 1 b. group 13 c. group 2 d. group 17 Lose 1 lose 3 lose 2 gain 1 11. Label each as forming ionic, covalent, or metallic bonds a. AlN b. CO2 c. Al foil d. H2O e. SnO d. CuF2 Ionic covalent metallic covalent ionic ionic 12. What is the formula when the following ions bond a. Magnesium and fluoride MgF2 b. Magnesium and oxide MgO c. Aluminum and bromide AlBr3 d. Sodium and oxide Na2O e. Barium and hydroxide Ba(OH)2 13. Which of the following would have the highest boiling point and why? H2O or H2S Water has hydrogen bonding holding the molecules together. Hydrogen sulfide has dipole-dipole which are not as strong 14. What kind of attractive forces must be overcome to a. Boil water b. Melt KCl c. Sublime(solid to gas) I2 d.Boil H2S Hydrogen bonding ionic London dispersion(van der waals) dipole-dipole 15. Nitrogen and carbon monoxide have almost equal masses. Explain why the boiling point of carbon monoxide is slightly higher than that of nitrogen It is polar so it has dipole-dipole forces where nitrogen only has London dispersion which is weaker.