Question Video: Identifying Endo- and Exothermic Reactions from Reaction Enthalpies Chemistry

A chemical reaction has a reaction enthalpy of +430 kJ/mol. Is it endothermic or exothermic?

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Video Transcript

A chemical reaction has a reaction enthalpy of positive 430 kilojoules per mole. Is it endothermic or exothermic?

So what we have here is an unknown chemical reaction where reactants are transforming to products and the change in enthalpy is positive. What this means is that because of the reaction, more energy must have entered the system than has left it. An endothermic reaction is a reaction where the energy in exceeds the energy out. This is usually accompanied by a decrease in the temperature of the surroundings. Meanwhile, an exothermic reaction is one where the energy released is greater than the energy absorbed. This is usually accompanied by an increase in the temperature of the surroundings.

Since the enthalpy change is positive, the enthalpy after the reaction is greater than the enthalpy before the reaction. The reaction is, by definition, endothermic even though we don’t know what the reactants and products are.

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