Homework 7 - 0.68 g/cm 3 and the enthalpy of combustion is...

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CHEMISTRY 201X: Homework #7 Due : Friday, November 9, 2007 “Thermochemistry” (Useful data can be found in Appendix C in Brown, LeMay, and Bursten, 10 th Edition) (1) (6 points) Large quantities of hydrogen are produced by reacting methane with steam at 1100 ° C. The process involves the following two reactions (1) Methane reacts with steam to produce hydrogen gas and carbon monoxide gas. (2) Carbon monoxide reacts with excess steam to produce hydrogen gas and carbon dioxide. (a) Write the balanced chemical equations for these two reactions. (b) Use bond enthalpies to estimate the enthalpy changes (in kJ) for your reactions. (c) Use standard heats of formation to calculate the enthalpy changes (in kJ) for these reactions. (2) (4 points) By walking 1 km, you use about 100 kJ of energy. This energy comes from the oxidation of foods, which is about 30% efficient. How much energy do you save by walking 1 km instead of driving a car that gets 8.0 km/L gasoline (19 miles/gal)? The density of gasoline is
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Unformatted text preview: 0.68 g/cm 3 and the enthalpy of combustion is − 48 kJ/g. (3) (8 points) Suppose 1.00 mole ice at − 30.0 ° C is heated at 1.00 atm pressure until it is converted to steam at 140 ° C. Calculate ∆ q , ∆ w , ∆ H , and ∆ E for this process. For ice, water, and steam, C P is 38, 75, and 36 J/mol ⋅ K, respectively, and can be taken to be approximately independent of temperature. ∆ H fus for ice is 6.007 kJ/mol, and ∆ H vap for water is 40.66 kJ/mol. Use the ideal gas law for steam, and assume that the volume of 1 mole of ice is negligible relative to that of 1 mole of steam. (4) (6 points) Consider the following acid-base reactions involving the strong base NaOH(aq): HNO 3 (aq) + NaOH(aq) ⎯→ NaNO 3 (aq) + H 2 O(l) HCl(aq) + NaOH(aq) ⎯→ NaCl(aq) + H 2 O(l) NH 4 + (aq) + NaOH(aq) ⎯→ NH 3 (aq) + Na + (aq) + H 2 O(l) (a) Calculate ∆ H ° for each reaction. (b) Compare the acid strengths of the three acids above based on your results in (a)....
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