CHEM 151 Lecture Notes - Lecture 12: Formaldehyde, Methanol, Abc Comedy

• School: University of Arizona
• Department: Chemistry
• Course: CHEM 151
• Professor: kumirov

Document Summary

A common signature of a chemical change is the release or absorption of energy. Energy is needed to separate a pair of bonded atoms. The energy provided is transformed into potential energy of the separated atoms. Heteronuclear bonds are stronger than homonuclear bonds (hydrogen is an exception h-h) A-a + b-b 2 a-b (weak bonds to stronger bonds = exothermic reaction = net energy release) 2 a-b-c 2 a + 2 b + c-c (endothermic reaction = stronger bonds to weaker bonds) Ch2o + o2 co2 + h2o (formaldehyde combustion) Ch4o + 1. 5 o2 co2 + 2 h2o (methanol combustion) Heat of reaction h is the difference in energy between bonds broken and bonds formed (exothermic is negative, endothermic is positive) Methane (least oxidized) methanol formaldehyde (most oxidized) Oxygen double bond is relatively weak bond, while the co (double bond) and oh bonds are strong.