Why the mass action law is not valid for very low temperatures?

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In summary, the mass action law is not valid for very low temperatures because the molecules have less kinetic energy and are less likely to collide, making the reaction rate much slower. It is typically valid within a temperature range of 300-1000 K, but this may vary depending on the specific reaction and concentration of reactants. There are exceptions where the mass action law may still hold true at low temperatures if the reaction is catalyzed or if there is a large concentration of reactants present. Temperature directly affects the equilibrium constant in the mass action law, with a decrease in temperature leading to a decrease in the equilibrium constant. However, the mass action law cannot be used to reliably predict reactions at very low temperatures as other factors such as activation
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Ger3
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why the mass action law is not valid for very low temperatures??

Hi,
In the context of semiconductors, I was asked why the mass action law is not valid for very low temperatures. I thought that it was valid, since for very low temperature it holds the non-degeneracy condition [tex] E_g >> k_B T [/tex] (I think so...). But maybe for some other reason it breaks. Does someone know why? Thanks!
 
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I am not sure, but perhaps it is related to the behavior of electrons in the lattice, which becomes more prominent at lower temperatures (or low energies)?
 

1. Why is the mass action law not valid for very low temperatures?

The mass action law is based on the assumption that all molecules in a reaction have enough energy to collide and react. However, at very low temperatures, the molecules have less kinetic energy and are less likely to collide, making the reaction rate much slower. This violates the principle of the mass action law.

2. What is the range of temperatures where the mass action law is valid?

The mass action law is typically valid within a temperature range of 300-1000 K. This range may vary depending on the specific reaction and the concentration of reactants.

3. Are there any exceptions where the mass action law is valid at low temperatures?

In some cases, the mass action law may still hold true at low temperatures if the reaction is catalyzed or if there is a large concentration of reactants present. This is because the catalyst provides an alternative pathway for the reaction to occur, or the high concentration of reactants increases the chances of collisions.

4. How does temperature affect the equilibrium constant in the mass action law?

The equilibrium constant in the mass action law is directly proportional to temperature. This means that as temperature decreases, the equilibrium constant also decreases. This is because at lower temperatures, the rate of the forward reaction decreases, while the rate of the reverse reaction increases, leading to a decrease in the equilibrium constant.

5. Can the mass action law be used to predict reactions at very low temperatures?

No, the mass action law is not a reliable tool for predicting reactions at very low temperatures. Other factors such as the activation energy and the presence of a catalyst must also be considered in order to accurately predict reactions at low temperatures.

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