15k h1 in the second step the reaction is carried out

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Unformatted text preview: the reaction enthalpy change. c) The temperature change observed in an adiabatic bomb calorimeter is always positive whenever an exothermic reaction takes place. d) The standard formation enthalpy of oxygen gas is equal to zero at all reaction temperatures. e) In an adiabatic bomb calorimeter experiment, we adjust the amount of reactants so the measured temperature change is large enough that it can be measured but small enough that isothermal conditions can be assumed when calculating standard reaction enthalpies. f) The standard formation enthalpy of iodine is only equal to zero when iodine is in the pure solid molecular state (I2(s)) under standard pressure. Question 7: (10 points) Using the thermodynamic data reported at 298.15K (shown below), determine the standard reaction enthalpy at 368.15K for the reaction: CH4(g) + 2 Cl2(g) à༎ CCl4(l) + 2 H2(g) o o Substance Cpm 298.15 K (J/K.mol) ΔfH 298.15 K (kJ/mol) CH4(g) - 74.8 35.3 Cl2(g) - - - 33.9 CCl4(l) - 128.4 131.3 H2(g) - - - 28.8 The standard reaction enthalpy is given at 298.15 K by: ΔRHo298.15 K (kJ/mol) = [ΔFHo298.15 K (CCl4(l)) + 2 ΔFHo298.15 K (H2(g))] – [ΔFHo298.15 K (CH4(g)) + 2 ΔFHo298.15 K (Cl2(g))] ΔRHo298.15 K (kJ/mol) = [- 128.4 kJ/mol] – [- 74.8 kJ/mol] ΔRHo298.15 K (kJ/mol) = - 53.6 kJ/mol Calculation of the standard reaction enthalpy at 368.15K can be carried out imagining a cycle where: In the first step, reactants are cooled isobarically from 368.15K to 298.15K (ΔH(1)). In the second step, the reaction is ca...
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This note was uploaded on 01/26/2014 for the course CHEM 3615 taught by Professor Aresker during the Spring '07 term at Virginia Tech.

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