Problem Set 3 problems Chem 3321 Fall, 2009 ∆ rH o = standard enthalpy of reaction ∆ f H o = standard enthalpy of formation ∆ r U o = standard ∆ U of the reaction 1. The molar heat capacity of ethane is represented in the temperature range of 298 K to 400 K by the empirical expression C p,m /(J K-1 mol-1 ) = 14.73 + 0.1272 (T/K). The corresponding expressions for C(s) and H 2 (g) are of the form C p,m (J K-1 mol-1 ) = a + bT + c/T 2 where a, b and c are 16.86, 4.77 and -8.54 for C(s) and 27.28, 3.26, and 0.50 for H 2 (g). Calculate the standard enthalpy of formation of ethane at 350 K from its value at 298 K. 2. The standard enthalpy for formation of the metallocene bis(benzene)chromium was measured in a calorimeter. It was found for the reaction Cr(C 6 fH 6 )(s) Cr(s) + 2C 6 H 6 (g) that ∆ r U o (583 K) = 8.0 kJ/mol. Find the corresponding reaction enthalpy and estimate the standard enthalpy of formation of the coumpound at 583 K. The constant pressure molar heat capacity of benzene is 140 J K
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