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.
