Which balanced equation represents an endothermic reaction? 1.)C+O2-> CO2
2.)CH4+2O2-> CO2+2H2O
3.)N2+3H2-> 2NH3
4.)N2+O2-> 2NO

N2+O2-> 2NO

Explanation:

An endothermic reaction refers to a reaction in which heat taken in. This implies that heat is usually absorbed by the reaction system. The enthalpy of reaction for an endothermic reaction is always positive.

The triple bond between two Nitrogen atoms in N2 gas is very strong due to its small size and the triple bond thus the nitrogen molecule has a high dissociation energy. This accounts for the large amount of energy required to break the triple bond between nitrogen atoms in the nitrogen molecule. This causes the oxidation of Nitrogen molecule to NO to be largely endothermic.

they are all solids.