Thermochemistry

The following problems are taken from T. L. Brown, H. E. Lemay, B. E. Bursten, & J. R. Burdge, Chemistry: The Central Science, Ninth Edition, Chapter 5.

34)  Consider the following reaction:        

       CH₃OH(g) CO(g) + 2H₂(g)          ΔH = +90.7 kJ

       (a) Is heat absorbed or evolved in the course of this reaction?

       (b) Calculate the amount of heat transferred when 1.60 kg of CH₃OH(g) are decomposed by this reaction at constant pressure.

       (c) For a given sample of CH₃OH, the enthalpy change of reaction is 64.7 kJ. How many grams of hydrogen gas are produced?

       (d) What is the value of ΔH for the reverse of the previous reaction? How many kilojoules of heat are released when 32.0 g of CO(g) reacts completely with H₂(g) to form CH₃OH(g) at constant pressure?

50) When a 3.88 g-sample of solid ammonium nitrate dissolves in 60.0 g of water in a coffee-cup calorimeter, the temperature drops from 23.0°C to 18.4°C. Calculate ΔH (in kJ/mol NH₄NO₃) for the solution process

        NH₄NO₃(s)   NH₄⁺(aq) + NO₃^-(aq)          

      Assume the specific heat of the solution is the same as that of pure water.

60) From the heats of reaction

      2H₂(g) + O₂(g) 2H₂O(g)           ΔH = -483.6 kJ          

                    3O₂(g) 2O₃(g)             ΔH = +284.6 kJ

      calculate the heat of reaction for

      3H₂(g) + O₃(g) 3H₂O(g)

72) Calculate the value of ΔH° for each of the following reactions:      

      (a) N₂O₄(g) + 4H₂(g) N₂(g) + 4H₂O(g)       

      (b) 2KOH(s) + CO₂(g) K₂CO₃(s) + H₂O(g)

      (c) SO₂(g) + 2H₂S(g) (3/8)S₈(s) + 2H₂O(g)

      (d) Fe₂O₃(s) + 6HCl(g) 2FeCl₃(s) + 3H₂O(g)

84) The heat of combustion of ethanol, C₂H₅OH(l), is -1367 kJ/mol. A batch of sauvignon blanc wine contains 10.6% ethanol by mass. Assuming the density of the wine to be 1.0 g/mL, what caloric content does the alcohol (ethanol) in a 6-oz glass of wine (177 mL) have?