Sonim

Sure, also I am posting the standard calorimeter the book is considering here. This is the direct translation of the paragraph: As we saw, the heat involved in a transformation can be determined using a calorimeter. However, for many reasons, the calorimeter can't be used to determine the heat for every chemical reaction. There are situations where the reaction can be too slow or fast, can be explosive, it can even occur simultaneously with others undesirable reaction, what makes it impossible to measure the enthalpy variation for a specific reaction. How can we determine the heat involved in these type of transformations?

I am brazilian, so you might have a little trouble understanding. So the book is called Química: Cotidiano e Transformações Parte II( Chemistry: Day by Day and Transformations). The first chapters are about solutions( density, molar concentration, etc) and colligatives properties, then we get to Thermochemistry. It starts with the concept of heat and talking about energy, later we get to endothermic and exothermic reactions. After all that, we are introduced to what is a calorimeter and Hess Law. I am posting the pic that says about the Hess Law.

This is not am homework problem, just an personal question. So, my book introduces Thermochemistry with the concept of heat and how a calorimeter works. After that, it explains the story behind Hess Law and says that one of the reasons it was created is because a calorimeter can't calculate fast chemical reactions, but it doesn't really say the problem with it. I am supposing the heat is not enough to evaporate the water in the calorimeter and the chamber where the reactions happens is centralized in the calorimeter. Maybe there is something to do with some heat leaving the calorimeter. Why can't it calculate fast chemical reactions? Won't the water in the calorimeter heat up or cool down after some time?