Calculating with Bond Energy - B

Get Problem Answer  |  Get New Problem  |  Go Problem Menu

Background

The energy consumed or liberated by a chemical reaction represents a deficit or an excess of energy that is a simple arithmetic sum of the reactant and product bond energies. This problem follows bond energy in a manner that is similar to balancing a checkbook. Textbook Discussion: Sections 7.12, pages 232. See Also: Example XII and P.O. 7.10, pages 234, and 248.

Problem

In the problem below, X, Y, and Z represent the symbols of three unknown elements. The following list gives the bond strengths of three diatomic molecules associated with the unknown elements X, Y, and Z at 25 degrees C:

AB = 32.2 kcal/mole       CD = 41.8 kcal/mole 

AD = 67.8 kcal/mole.       CB = 51.2 kcal/mole. 

Based on this bond strength information, calculate the value of Q in the following thermochemical equation:

     AD (g) + CB (g) ---> AB (g) + CD (g) Q = ? kcal @ 25 degrees C