# Can Calorimeters Measure Enthalpy Variation of Fast Reactions?

• Sonim
In summary, the conversation discusses the use of Hess' Law to measure the enthalpy variation of reactions that cannot be measured using a calorimeter. The question is raised as to why a calorimeter cannot be used to measure the enthalpy variation of fast reactions, and the other person suggests that there are ways to delay reactions. Both agree that while very slow reactions may be a problem, there should not be major issues with fast reactions.
Sonim
TL;DR Summary
Enthalpy , Calorimeter and Hess Law Question Related
First of all this is a question that I had while reading some concepts of my book, so this isn't a homework question. I have started reading the thermochemistry chapter of my book, and it shows the story of Hess' Law and says that it was created is because a calorimeter can't be used to measure the enthalpy variation of too slow reactions, explosive reactions, fast reaction and multi-step reactions. Why can't it be used to calculate the enthalpy variation of fast reactions ?

What are your thoughts on this?

berkeman
Actually, I think the opposite. There are ways to delay reactions, so this shouldn't be a problem. Maybe it lies on the fact that fast reactions releases/absorbs heat too fast, which results in the increase of heat flow. However, it shouldn't be a problem too, because the termometer in the calorimeter would release/absorb more heat in less time as well. Have you got any idea?

I agree with you on the fast reactions. However, on very slow reactions, no one has the time to wait days or weeks or years for the reaction to reach equilibrium. But, otherwise, like you, I don't see major problems.

## 1. What is a calorimeter?

A calorimeter is a scientific instrument used to measure the amount of heat released or absorbed during a chemical reaction. It typically consists of a container, known as a bomb, where the reaction takes place, and a thermometer to measure the temperature change.

## 2. How does a calorimeter measure enthalpy variation?

A calorimeter measures enthalpy variation by recording the change in temperature of the reaction mixture. The enthalpy change is then calculated using the equation Q = mcΔT, where Q is the heat released or absorbed, m is the mass of the reaction mixture, c is the specific heat capacity, and ΔT is the change in temperature.

## 3. Can a calorimeter accurately measure enthalpy variation of fast reactions?

Yes, a calorimeter can accurately measure enthalpy variation of fast reactions. However, it is important to use a calorimeter with a high sensitivity thermometer and a fast response time to accurately capture the temperature change during the reaction.

## 4. What are the limitations of using a calorimeter to measure enthalpy variation of fast reactions?

One limitation of using a calorimeter to measure enthalpy variation of fast reactions is that the heat released or absorbed may not be evenly distributed throughout the reaction mixture, leading to inaccurate results. Additionally, the heat capacity of the calorimeter itself may affect the accuracy of the measurement.

## 5. Are there any alternative methods for measuring enthalpy variation of fast reactions?

Yes, there are alternative methods for measuring enthalpy variation of fast reactions, such as using a differential scanning calorimeter (DSC) or a reaction calorimeter. These instruments have faster response times and can provide more accurate measurements for fast reactions.

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