F11-1251-Exam_4A_Key

1combustionis

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Unformatted text preview: 1070 CC 812 [4(799 kJ/mol) + 4 (463 kJ/mol)] CH 413 OO 142 +1 correct answer O=O 498 = 3761 kJ/mol 5048 kJ/mol = 1287 kJ/mol OH 463 ‐1 any missing units 4 (c) Why does your value of ∆Hrxn make sense? +1 combustion The chemical equation describes a combustion reaction. +1 combustion is Combustion reactions are exothermic and have negative H values. exothermic 2 2 A 3. (a) Draw three valid Lewis Structures for CO32‐ that obey the octet rule. Be sure to label all non‐zero formal charges on their respective atoms, and use brackets to indicate the overall charge. For each structure: +1 correct connectivity, bonds, and lone pairs +1 correct formal charge and brackets 1 no resonance arrows 6 (b) Consider the following bond lengths: C‐O, 143 pm; C=O, 123 pm; CO, 109 pm. In the CO3 ion, all three C‐O bonds have identical bond lengths of 136 pm. Explain this, using the data from the bond lengths above. The carbonate ion exhibits resonance. +1 resonance structures The actual structure is a...
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