Combustion reactions always result in the formation of water. What other types of chemical reaction may result in the formation of water? What are some examples of these reactions?

Neutralisations also result in the formation of water. e.g. ##HCl## + ##NaOH## --> ##NaCl## + ##H_2O## or ##MgO## + ##2HCl## --> ##MgCl_2## + ##H_2O##

Condensation reactions (may) result in the formation of water. e.g. ##CH_3COOH## + ##CH_3OH## --> ##CH_3COOCH_3## + ##H_2O## (this example is also an esterification - these produce water too)

Oxidation of alcohols to aldehydes or ketones also produces water e.g. ##CH_3CH_2OH## + ##[O]## --> ##CH_3CHO## + ##H_2O##

... but combustion reactions DON'T always result in the formation of water. Combustion of hydrocarbons and similar organic molecules does, but what about combustion of magnesium, or sulphur? The only product is magnesium oxide, or oxides of sulphur. Nitrogen is combusted at high temperatures producing nitrogen oxides. We can therefore say that combustion produced the oxidation products of whatever is burnt, but not that this will always be water.