Name: Thermochemistry Worksheet #1 1. The reaction of magnesium with sulfuric acid was carried out in a calorimeter. This reaction caused the temperature of 27.0 grams of liquid water, within the calorimeter, to raise from 25.0C to 76.0C. Calculate the energy associated with this reaction. 2. The reaction of zinc with nitric acid was carried out in a calorimeter. This reaction caused the temperature of 72.0 grams of liquid water, within the calorimeter, to raise from 25.0C to 100.C. Calculate the energy associated with this reaction. 3. A 4.00 gram sample of solid gold was heated from 274K to 314K. How much energy was involved? 4. The reaction of magnesium with hydrochloric acid carried out in a calorimeter caused the temperature of water to change from 25.0C to 36.0C. In this reaction 3760J of energy was released. What mass of water was present? 5. The reaction of magnesium oxide with hydrochloric acid carried out in a calorimeter caused the temperature of water to change from 25.0C to 46.0C. In this reaction 4860J of energy was released. What mass of water was present? 6. A piece of solid gold was heated from 274K to 314K. 35.7J of energy was needed to raise the temperature. What mass of gold was present? Use Hf values (table found in notes) to solve the following problems. 7. Determine the H for each of the following reactions. Classify each reaction as either exothermic or endothermic. a. C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(g) H = ? kJ/mol b. H2 (g) + Cl2(g) 2HCl(g) H = ? kJ/mol c. CH4(g) + 2O2(g) CO2(g) + 2H2O(g) H = ? kJ/mol d. 2F2(g) + 2H2O(l) 4HF(g) + O2(g) H = ? kJ/mol e. Na2O(s) + SO2(g) Na2SO3(s) H = ? kJ/mol 8. Use Hf values to solve the following problems. The production of steel from iron involves the removal of many impurities in the iron ore. The following equations show some of the purifying reactions. Calculate the enthalpy (H) for each reaction. a. 3C(s) + Fe2O3(s) 3CO(g) + 2Fe(s) H = ? kJ/mol b. 3Mn(s) + Fe2O3(s) 3MnO(s) + 2Fe(s) H = ? kJ/mol c. 12P(s) + 10Fe2O3(s) 3P4O10(s) + 20Fe(s) H = ? kJ/mol d. 3Si(s) + 2Fe2O3(s) 3SiO2(s) + 4Fe(s) H = ? kJ/mol e. 3S(s) + 2Fe2O3(s) 3SO2(g) + 4Fe(s) H = ? kJ/mol Thermochemistry Worksheet #2 Hess’s Law Problems 1. Calculate the heat of the reaction for the following reaction: 2F2(g) + 2H2O(l) 4HF(g) + O2(g) H = ? kJ/mol Use heat of formation values. Is this reaction exothermic or endothermic? Answer: -521.6kJ/mol 2. Calculate the heat of the reaction for the following reaction: Na2O(s) + SO2(g) Na2SO3(s) H = ? kJ/mol Use heat of formation values. Is this reaction exothermic or endothermic? Answer: -390.0kJ/mol 3. Given the following two reactions and enthalpy data: CH2CO(g) + 2O2(g) 2CO2(g) + H2O(g) H = 981.1 kJ CH4(g) + 2O2(g) CO2(g) + 2H2O(g) H = 802.3 kJ calculate the enthalpy change for the reaction in which methane and oxygen combine to form ketene, CH2CO, and water. 2CH4(g) + 2O2(g) CH2CO(g) + 3H2O(g) H = ? kJ/mol Answer: -623.5kJ/mol 4. Calculate the reaction enthalpy for the following reaction. Is this reaction exothermic or endothermic? 5CO2(g) +Si3N4(s) 3SiO(s) +2N2O(g) + 5CO(g) H = ? kJ/mol Answer: 2024 kJ/mol Use the following equations and data. CO(g) + SiO2(s) SiO(g) + CO2(g) H = +520.9 kJ 8CO2(g) + Si3N4(s) 3SiO2(s) + 2N2O(g) + 8CO(g) H = +461.05 kJ 5. Calculate H for the reaction of calcium oxide and sulfur trioxide. Is this reaction exothermic or endothermic? CaO(s) + SO3(g) CaSO4(s) H = ? kJ/mol Use the following equations and data. H2O(l) + SO3(g) H2SO4(l) H = 132.5 kJ/mol H2SO4(l) + Ca(s) CaSO4(s) + H2(g) H = 602.5 kJ/mol Ca(s) + ½ O2(g) CaO(s) H = 634.9 kJ/mol H2(g) + ½ O2(g) H2O(l) H = 285.8 kJ/mol 6. Find the enthalpy of the reaction of magnesium oxide with hydrogen chloride. MgO(s) + 2HCl(g) MgCl2(s) + H2O(l) H = ? kJ/mol Answer:-141.1kJ/mol Use the following equations and data. Mg(s) + 2HCl(g) MgCl2(s) + H2(g) H = 456.9 kJ/mol Mg(s) + ½ O2(g) MgO(s) H = 601.6 kJ/mol H2O(l) H2(g) + ½ O2(g) H = +285.8 kJ/mol Thermochemistry Substance Hf (kJ/mol) Hf and specific heat values found in notes or in table provided. C2H2(g) 228.2 1. Calculate the heat of the reaction for the following reaction: Ag2S(s) -32.59 2C2H2(g) + 5/O2(g) 4CO2(g) + 2H2O(g) H = ? kJ/mol AgCl(s) -127.01 Solve by writing formation equations for each reactant and product and H2S(g) -23.9 using the H values for each. Is the reaction exothermic or endothermic? Ca(OH) (s) -983.2 Answer: -2514.0kJ/mol (exothermic) 2 CO(g) -110.5 2. Calculate the H value heat for the following reaction: Ag2S(s) + 2HCl(g) 2AgCl(s) + H2S(g) H = ? kJ/mol Solve by writing formation equations for each reactant and product and using the H values for each. Answer: -60.73kJ/mol (exothermic) 3. Calculate the H value heat for the following reaction: Ca(OH)2(s) CaO(s) + H2O(g) H = ? kJ/mol Solve by writing formation equations for each reactant and product and using the H values for each. Answer: 106.5kJ/mol (endothermic) 4. Calculate the H value heat for the following reaction: Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2(g) H = ? kJ/mol Solve by writing formation equations for each reactant and product and using the H values for each. Answer: 269.4kJ/mol (endothermic) 5. Find the enthalpy of the reaction of magnesium oxide with hydrogen chloride. MgO(s) + 2HCl(g) MgCl2(s) + H2O(l) H = ? kJ/mol Answer:-141.1kJ/mol Use the following equations and data. Mg(s) + 2HCl(g) MgCl2(s) + H2(g) H = 456.9 kJ/mol Mg(s) + ½ O2(g) MgO(s) H = 601.6 kJ/mol H2O(l) H2(g) + ½ O2(g) H = +285.8 kJ/mol 6. The reaction of magnesium with sulfuric acid was carried out in a calorimeter. This reaction caused the temperature of 55. grams of liquid water, within the calorimeter, to raise from 1.0C to 28.C. Calculate the energy associated with this reaction. Answer: 6200J 7. A 22..0 gram sample of solid gold was heated from 200.K to 300.K. How much energy was involved? Answer: 284J .