The standard enthalpy of formation of gaseous H2O at 298 K is -241.82 kJ/mol. What is the ΔH at 373 K given the following values of the molar heat capacities at constant pressure? H2O(g) = 33.58 J K-1 mol-1; H2(g) = 29.84 J K-1 mol-1; O2(g) = 29.37 J K-1 mol-1 H2(g) + ½ O2(g) → H2O(g)

Determine the  ΔH of formation for sulfur trioxide gas if: 2 SO2 (g) +  O2 (g) --> 2 SO3 (g)    ΔH = -300 kJ SO2 (g)  -->    O2 (g) + S (s)    ΔH = 200 kJ The standard state of sulfur is S  (s).         - 350 kJ/mol     -500 kJ/mol     +200 kJ/mol     +100 kJ/mol     -400 kJ/mol

7) Calculate the change in internal energy (AE) for a system that is giving off 25.0 kJ of heat and is changing from 12.00 L to 6.00 L in volume at 1.50 atm pressure. (Remember that 101.3 J = 1 L'atm) A) +25.9 kJ B) -16.0 kJ C) -25.9 kJ D) -24.1 kJ E) 937 kJ Answer: D Diff: 2 Page Ref: 6.4

Calculate ΔHf for HCN(g) at 25°C, given the following related reaction at 25°C, 2 NH3(g) + 3 O2(g) + 2 CH4(g) ---> 2 HCN(g) + 6 H2O(g); ΔHrxn = -870.8 kJ and the heats of formation of some species are ΔHf = -80.3 kJ/mol for NH3(g), -74.6 kJ/mol for CH4, and -241.8 kJ/mol for H2O(g). Answers are in kJ/mol.

A styrofoam calorimeter contains 60.0 mL of o.750 M H.C,H 0, at 3 6 22.8°C. When 9.83 g NaHCO, is added to the calorimeter, the temperature of the resulting solution decreases to a minimum of 5.1°C. The reaction that occurs is: HаCоН,О-(aд) + 3 NaHCO3(aq) > NagCgHsО7(ag) + 3 СО2(9) + 3 Н-0(1) AHreaction = ??? What is the (experimental) enthalpy change for this reaction, AH ? (Use the total mass of reaction solution and 4.18 J/(g °C) for the specific heat of the solution in your calculations.) kJ/mol

4. What mass of propane must be burned to supply 700. kJ as heat? The thermochemical equation for the combustion of propane is: C3H8(g) + 5 O2(g) → 3 CO2(g) + 4H₂O(1) AH°-2220. kJ