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T7-Questions

T7-Questions - TUTORIAL#9 November 19th 2007 Solutions...

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CHEM 1A03 TUTORIAL #9 November 19 th , 2007 Solutions – Chapter 7 Correction to Q 4 _____________________________________________________________________ 1. From the course notes, we had an expression for work: gases w P V n RT = ! " = !" From this, and our expressions for enthalpy and internal energy, we can re-write Δ H as: V U q w ! = + H U P V ! = ! + ! gases H U n RT !" = " + " Based on this expression, calculate the difference between Δ H and Δ U for the combustion of octane at 298K. 2. Nitric Acid is produced by the Ostwald Process in the gas phase at elevated temperature and pressure, which is an industrially important chemical widely used in the fertilizer industry, as discussed in Chapter 15. Based on the balanced net reaction below, and the given heats of formation, all in kJ/mol, determine whether this overall process is exothermic or endothermic, and estimate the energy change per mole of HNO 3 formed. 3. When treating a hypothermia victim, it is important to both raise the body temperature, and dry the body. Calculate the enthalpy change required to for a person to warm their body (mass 70kg) from 34 o C to 37 o C, and dry it, using body heat, by evaporating 500g of water from the skin surface (phase change). 4. Calculate the total calorie content for each burger patty (no condiments, oil, bread, etc.) Assume an average energy content of 16.74 kJ/g for both protein & carbohydrates, and 37.66 kJ/g for fats. Which burger has the lowest total calorie content? Explain why. What is the percentage of the average recommended daily calorie intake for each burger assuming a person with a sedentary lifestyle of 2000 kcal/day?

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CHEM 1A03 TUTORIAL #9 November 19 th , 2007 Solutions – Chapter 7 Correction to Q 4 _____________________________________________________________________ 5. Use enthalpies of formation (found in Appendix D of your textbook) to calculate the standard enthalpy change for the following reaction at 298K: 2 C 2 H 6 (g) + 7 O 2 (g) 4 CO 2 (g) + 6 H 2 O(l) 6. Coal and natural gas are both fuels used for home heating. Assuming that coal is pure graphite and that natural gas is pure methane, and that graphite and methane have the same cost per gram, decide which of these two fuels is the more economical for heating a home. (Assume that gaseous water is produced when methane burns, and that both combustion reactions are complete.) Use standard formation enthalpies from Appendix D of your textbook. 7. Calculate the enthalpy change, in kJ, at 25
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T7-Questions - TUTORIAL#9 November 19th 2007 Solutions...

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