Question

How can I tell whether a reaction is exothermic or endothermic just by looking at the formula? ex. 21.0 kcal/mole + C(solid) + 2S(solid) --> CS(sub 2) (liquid)

Answer 1

when energy is included in a reaction, whether it is used as a reactant or product will tell you if the reaction is endothermic or exothermic. A reaction that uses energy as a reactant must draw it in from the surroundings, so the reaction will be ENDOthermic. A reaction that producexs heat as a product will send it out into the surroundings, and the reaction will be EXOthermic