Reaction energy for polymerization of polychloroprene

[d.arbitman]

Homework Statement

Please see attached for problem statement and table of bond energies. My chemistry background is awful and this is from a materials science textbook. The question is, how would I approach/solve 2.31 (only parts b and c).

Homework Equations

The Attempt at a Solution

We go from two double bonds (C= C) and a single bond (C - C) to two single bonds (C-C) and one double bond (C= C)
(2*3.7E5 + 6.8E5) - (2*6.8E5) = 60 kJ/mole

The molecular mass of the 'mer' is 88.53 g/mole.
1kg/88.53g = 11.30 moles
60 kJ/mole * 11.30 mole = 678 kJ

I know both of these are the correct answer, but I just need verification of my problem setup.

Thanks.

 

[nate808]

I would approach this problem by first understanding the concept of bond energies and how they relate to the stability of molecules. In this case, we are dealing with the conversion of double bonds to single bonds, which will result in a more stable molecule.

To solve part b, we need to calculate the energy released from breaking the two double bonds and forming two single bonds. Using the table of bond energies, we can see that the energy required to break a double bond is 6.8E5 kJ/mole, and the energy released from forming a single bond is 3.7E5 kJ/mole. So for two double bonds, we have (2*6.8E5) - (2*3.7E5) = 6.8E5 kJ/mole.

To solve part c, we need to calculate the total energy released from breaking the two double bonds and forming one double bond. Using the same concept as part b, we can see that the energy required to break two double bonds is (2*6.8E5) = 13.6E5 kJ/mole, and the energy released from forming one double bond is (1*6.8E5) = 6.8E5 kJ/mole. So the total energy released is 13.6E5 - 6.8E5 = 6.8E5 kJ/mole.

Your calculations and setup for both parts b and c are correct. However, as a scientist, it is important to always double-check our work and make sure we are using the correct units and following the correct mathematical operations. In this case, the units for bond energies are kJ/mole, so we should not convert to moles before calculating the energy released. So for part c, the correct calculation would be (2*6.8E5) - (1*6.8E5) = 6.8E5 kJ/mole.

Overall, your approach and solution to this problem are valid, but as a scientist, it is important to always double-check our work and make sure we are using the correct units and following the correct mathematical operations.