2nahco3(s) + 129kj → na2co3(s) + h2(g) + co2(g) what is the best description of the energy exchange in this reaction? a) when heated, baking soda decomposes. this is an exothermic reaction. b) when heated, baking soda decomposes. this is an endothermic reaction. c) baking soda absorbs energy when heated. it is an exothermic reaction. d) baking soda releases energy when it decomposes. it is an endothermic reaction.