## Chemistry and Chemical Reactivity (9th Edition)

One $O\equiv C$ bond is broken, converting it to a O=C bond, one O-C bond is broken but one is formed along with a C-C bond, so overall: $H_{O\equiv C}-H_{O=C}-H_{C-C}=$ $1046-745-346=-45\ kJ/mol$ It's an exothermic reaction.