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bjoyful
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Homework Statement
Use the bond energies (in Table 4.2) to calculate the energy changes associated with each of these reactions. In each case indicate whether the overall reaction is endothermic or exothermic. Be sure to show your calculation work.
2. Homework Equations [/b
The Attempt at a Solution
A. H2(g) + O2(g) -----> H2O2(g) Answer: H2 is H-H (+436) and O2 is O=O (+498). Total energy in breaking bonds is 934 kJ. H2O2 is H-O=O-H (-467,-498,-467). Total in making bonds is -1432 kJ. Therefore, the net energy change is -498kJ, with the overall reaction being exothermic.
B. 2H2(g) + O2(g) -----> 2H2O(g) Answer: 2H2 is H-H (+436), H-H (+436). O2 is O=O (+498). Total energy in breaking bonds is +1370kJ. 2H20 is H-O-H (-467x2), H-O-H (-467x2). Total energy in making bonds is -1868kJ. Therefore, the net energy change is
-498kJ, with the overall reaction being exothermic.
C. 2H2(g) + CO(g) -----> CH3OH(g). Answer: H-H (+436), H-H (+436). CO is C=O (+1073). Total in breaking bonds is +1208. CH3OH is C-H (-416x3), C=O (-803), O-H (-467)
I find it strange that I came up with exothermic for all three of these...