Is this reaction endothermic or exothermic? Gas burning in a Bunsen burner: #C_2H_6(g) + 3.5O_2(g) -> 2CO_2(g) + 3H2O(g) + 2855kJ#

1 Answer
Dec 11, 2016

Answer:

Clearly, the reaction is #"exothermic"#.

Explanation:

You are burning ethane; normally, the gas supplied to homes and labs is methane, #CH_4#.

#CH_4(g) +2O_2(g) rarr CO_2(g) +2H_2O(g)#

The stability of the #C=O# and #O-H# bonds means that energy is released upon their formation, and the reaction is #"exothermic"#. Most combustion reactions, e.g burning coal, burning hydrocarbon in an internal combustion engine, lighting a barbeque, are exothermic. The way the problem was set out, with energy listed as a #"PRODUCT"# also suggests that energy was a product, a result of reaction.

Usually, when energy output is reported, the energy associated with an exothermic reaction would be quoted as negative, i.e.

#CH_4(g) +2O_2(g) rarr CO_2(g) +2H_2O(g)# #;DeltaH^@ =-2855*kJ*mol^-1#