Thermochemistry Worksheet

Thermochemistry Worksheet 1. How much heat, in calories, is released or absorbed if a 15.0 g sample of copper is converted from (a) the solid to liquid state. (b) the gas to the liquid state. For copper m.p. = 1084 °C ; b.p. = 2927 °C; ∆Hfus = 206 J/g, ∆Hvap = 4.7 kJ/g 2. How much heat is absorbed or released if a 12.5 g sample of aluminum changes temperature from 25.0 to 87.5 °C? The specific heat capacity of aluminum is 0.900 J/g.K 3. What was the mass of a sample of water if the addition of 4.28 x 103 joules raised the temperature of the sample from 22.0 0C to 34.5 0C? 4. Calculate the total heat energy (in kilojoules, kJ) needed to convert 25.0 g of ice at 0.0 °C to steam at 130.0 °C. 5. Calculate the total heat energy, q, (in kJ) when 50.0 g of steam at 100.0 °C converts to ice at 0.0 °C. 6. A 245 gram sample of a metal at 99.5 °C was added to a 114 gram sample of water in a perfect calorimeter. The original temperature in the calorimeter was 23.5 °C. The final temperature of the metal-water mixture was 35.6 °C. Calculate the specific heat of this metal in joules per gram per Kelvin. 7. Calculate the final temperature, in °C, that results from mixing 245 grams of cobalt, specific heat 0.446 J/g.K, at 142 °C with 106 grams of water at 24.8 °C. 8. Consider the thermochemical equation below: C6H12O6 (s) + 6 O2 (g) → 6 CO2 (g) + 6 H2O (g) ∆rH° = -2803 kJ (a) Is this reaction endothermic or exothermic? (b) How much heat is absorbed or released when 9.22 grams of glucose C6H12O6 in your body reacts, according to the following equation? (c) How many grams of CO2 will be produced if sufficient glucose is burned to produce 3450 kJ heat energy? 9. Consider the thermochemical equation below: 4 NO (g) + 6 H2O (l) → 4 NH3 (g) + 5 O2 (g) ∆rH° = 1170 kJ (a) Is this reaction endothermic or exothermic? (b) How much heat will be absorbed or released if 10.0 g of NO is reacted with 10.0 g H2O? (c) How much heat energy is required to produce 500. g of NH3? 10. When 6.50 g sample of solid sodium hydroxide dissolves in 100.0 g of water in a coffee cup calorimeter, the temperature rises from 21.6 °C to 37.8 °C. (a) Is the formation of the sodium hydroxide solution exothermic or endothermic? Why? (b) Calculate ΔH (in kJ/mol NaOH) for the solution process. Assume that the specific heat of the solution is the same as that of pure water. 11. In a coffee-cup calorimeter, 100.0 mL of 1.0 M NaOH and 100.0 mL of 1.0 M HCl are mixed. Both solutions were originally at 24.6 °C. After the reaction, the temperature is 31.3 °C. What is the enthalpy change for the neutralization of one mole of HCl by NaOH? (Hint: assume that the density of the mixture is 1.00 g/mL, and the specific heat of the mixture is the same as water) 12. In a coffee-cup calorimeter, 100.0 mL of distilled water, originally at 22.8 °C, is combined with 13.95 g of ice at 0.00 °C. After the ice has melted, the temperature is 12.5 °C. What is the heat capacity of the coffee cup? Assume the density of water is 1.00 g/mL. Note: c (ice) = 2.108 J/g.K ; c (water) = 4.184 J/g.K ; c (steam) = 1.996 J/g.K 13. When a 7.68 g sample of sulfur (S8) is burned in a bomb calorimeter with excess oxygen, the temperature increases from 20.34 °C to 36.75 °C. The calorimeter contains 815 g of water, and the heat capacity of the bomb is 923 J/K. Calculate ΔU for the reaction in kJ/mol S8. 14. Calculate the ∆rH0 for the following reaction: 2 H2O2 (l) → 2 H2O (g) + O2 (g) You are given these two equations: 2 H2 (g) + O2 (g) → 2 H2O (l) ∆rH0 = -572 kJ H2 (g) + O2 (g) ∆rH0 = -188 kJ → H2O2 (l) 15. Calculate the ∆rH for the following reaction: 0 NO (g) + O (g) → NO2 (g) You are given these three equations: O2 (g) → 2 O (g) ∆rH0 = +498.4 kJ 2 O3 (g) → 3 O2 (g) ∆rH0 = -285.3 kJ NO (g) + O3 (g) → NO2 (g) + O2 (g) ∆rH0 = -199.0 kJ 16. Write the formation reactions for the following: (a) H2O2 (l) (b) Potassium sulfate (c) Lithium nitrate (d) Liquid Glycerol (C3H8O3) (e) Ammonia (f) N2O5 (a solid) 17. Calculate the ∆rH0 from the ∆fH0 (use Appendix L of textbook) for the following reactions: (a) PbO (s) + CO (g) -------> Pb (s) (b) SiH4 (g) + 2 O2 (g) -------> + CO2 (g) SiO2 (s) + 2 H2O (l) (c) 4 FeS2 (s) + 11 O2 (g) -------> 2 Fe2O3 (s) + 8 SO2 (g)