Assigned Problems Set_2, answers

Assigned Problems Set_2, answers - Chemistry 2080 Spring...

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Chemistry 2080 Spring 2011 Problem Set #2 - due date: Friday February 11th at 2 pm Name:___ KEY__________ Lab TA Name:__________________ Lab Day/Time:______________________ 1) Calculate the standard enthalpy change for producing ethane (C 2 H 6 ) from its elements: 2C(s) + 3H 2 (g) –––––––> C 2 H 6 (g) Δ H° = ??? (In practice this reaction would be difficult to run as there would be many products) We know the standard enthalpy changes for the following combustion reactions: a) C 2 H 6 (g) + 7 /2 O 2 (g) –––––> 2CO 2 (g) + 3H 2 O(l) Δ H° = – 1,559.7 kJ b) C(s) + O 2 (g) ––––––> CO 2 (g) Δ H° = – 393.5 kJ c) H 2 (g) + 1 /2 O 2 (g) ––––––> H 2 O(l) Δ H° = – 285.8 kJ To solve the problem, we must rearrange the above equations and multiply . . . . (b) x 2 2C(s) + 2O 2 (g) ––––––> 2CO 2 (g) Δ H° = 2(– 393.5)kJ = – 787.0 kJ (a) x (-1) 2CO 2 (g) + 3H 2 O(l) ––––> C 2 H 6 (g) + 7 /2 O 2 (g) Δ H° = +1,559.7 kJ
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