Which reaction is endothermic?
2brcl mc019-1.jpg br2 + cl2 + 29.3 kj
2h2 + o2 mc019-2.jpg 2h2o + 572 kj
c + o2 mc019-3.jpg co2 + 394 kj
n2o4 + 59 kj mc019-4.jpg 2no2

An endothermic reaction is that which takes in heat or energy in order for the reaction to proceed. In the chemical equation, heat appears in the reactant side. From the given choices, there is only one in which heat is in the reactant side. Thus, the answer is letter D. 

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