CHEM
Problem Set 5

# C consider the industrial process for the production

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(c) Consider the industrial process for the production of acrylonitrile, the starting material used in the manufacture of acrylic fibers (> 2 million pounds/year in the US): HCCH ( g ) + HCN ( g ) CH 2 =CHCN ( g ) Calculate S°, H°, and G° for this addition reaction at 298 K from the tabulated data on page 1. Is the entropic data consistent with that discussed above? Chem 33, Kanan & Stack, 2012, PS 5; pg 2

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3. A reduction reaction such as the reduction of formaldehyde to methanol with H 2 (g) can formally be considered an addition reaction. H 2 C=O ( g ) + H 2 ( g ) CH 3 OH ( g ) (a) Bond dissociation energies can be used to calculate a rough estimate of the enthalpy change for a reaction. The energy released in forming new bonds can balance or exceed the energy needed to break bonds during a chemical transformation. Using the average bond enthalpies given, calculate the enthalpy change for the reaction above. (kcal mol -1 ; C=O 178; C–O 93; H–H 104; C–H (for methanol) 97; O–H 104). (b) Calculate S°, H°, and G° for the reduction of formaldehyde addition reaction with all reagents and products in the gas phase at 298 K. (c) Consider the more realistic reduction reaction of formaldehyde to liquid methanol: H 2 C=O ( g ) + H 2 ( g ) CH 3 OH ( l ) Calculate S°, H°, and G° for this reaction. Before performing any calculations, try to anticipate the differences in the values of S° and H° for this reaction as compared to the reaction in part (b). Chem 33, Kanan & Stack, 2012, PS 5; pg 3
(d) The difference between part (b) and part (c) is just a phase change from CH 3 OH( g ) to CH 3 OH( l ). Certainly one would expect that condensation of a gas to a liquid would be associated with a negative entropy (a loss of disorder).

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• Spring '10
• Dunremember
• Reaction, Chem, Chemical reaction

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