The Hückel determinant for naphthalene, C 10 H 8 , is to be stated. Concept introduction: According to the Hückel approximation of the π molecular orbitals, the sigma bonds and pi bonds are considered separately. Also, it is assumed that π molecular orbitals are the linear combinations of 2 p orbitals from the different carbon atoms. From the linear variation theory, the energies of the π molecular orbitals can be determined by using the secular determinant.

Question

Q2. Consider the hydrogenation of ethylene C2H4 + H2 = C2H6 The heats of combustion and molar entropies for the three gases at 298 K are given by: C2H4 C2H6 H2 AH comb/kJ mol‍¹ -1395 -1550 -243 Sº / J K¹ mol-1 220.7 230.4 131.1 The average heat capacity change, ACP, for the reaction over the temperature range 298-1000 K is 10.9 J K¹ mol¹. Using these data, determine: (a) the standard enthalpy change at 800 K (b) the standard entropy change at 800 K (c) the equilibrium constant at 800 K.

Answer 1

Question

Chapter 15, Problem 15.51E

Interpretation Introduction

Interpretation:

The Hückel determinant for naphthalene, C10H8, is to be stated.

Concept introduction:

According to the Hückel approximation of the π molecular orbitals, the sigma bonds and pi bonds are considered separately. Also, it is assumed that π molecular orbitals are the linear combinations of 2p orbitals from the different carbon atoms. From the linear variation theory, the energies of the π molecular orbitals can be determined by using the secular determinant.

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Q2. Consider the hydrogenation of ethylene C2H4 + H2 = C2H6 The heats of combustion and molar entropies for the three gases at 298 K are given by: C2H4 C2H6 H2 AH comb/kJ mol‍¹ -1395 -1550 -243 Sº / J K¹ mol-1 220.7 230.4 131.1 The average heat capacity change, ACP, for the reaction over the temperature range 298-1000 K is 10.9 J K¹ mol¹. Using these data, determine: (a) the standard enthalpy change at 800 K (b) the standard entropy change at 800 K (c) the equilibrium constant at 800 K.

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