Reaction rates, temperature, and thermal energy

In summary, the conversation discusses the relationship between reaction rates and temperature in exothermic reactions. It is explained that while increasing temperature will shift the equilibrium to the reactants, it will also increase the rate of collision between molecules and therefore increase the overall rate of the reaction. The concept of Le Chatelier's principle is mentioned as well as the importance of maintaining the ratio between forward and reverse rates for maintaining equilibrium.
  • #1
brake4country
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Homework Statement


Hi there. My question is more for clarification than a homework question. In my studies, I noticed that my MCAT study manual provides problems relating reaction rates and the effect that temperature and thermal energy have on a reaction. For example, a question asks: in an exothermic reaction, what affects the ratio of the forward rate to the reverse rate?

Homework Equations

The Attempt at a Solution


The correct answer is: removing thermal energy from the system. This answer makes sense. But, in another similar problem, the question is based on what would happen if the temperature is increased. One would think that it would shift the equilibrium to the reactants in an exothermic reaction. What am I missing here? How can the rates of both the forward and reverse be increased when temperature is increased? Thanks in advance.
 
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  • #2
It is true that the reaction will shift to the reactants due to Le Chatelier's principle, however when you increase the temperature, the reactant and product molecules will gain energy and move more vigorously. The rate of collision between the molecules increases. Thus even though the equilibrium does shift to the left, the rate increases because the molecules gain energy and make the chemical reaction occurs more rapidly.
 
  • #3
I see. Temperature will increase the the forward rate of a reaction even if it is exothermic. Removing thermal energy from an exothermic reaction will affect the ratio of the forward rate to the reverse rate by shifting it toward the products, right? I think I am getting the hang of this. I was confusing what affect temperature would have on a reaction and how removing thermal energy would affect it. Two different questions with different consequences.
 
  • #4
Yup you are right =) le chatelier principle is all about achieving equilibrium while rate of reaction can be explained through kinetic theory of particles.
 
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  • #5
brake4country said:
How can the rates of both the forward and reverse be increased when temperature is increased?

It is not absolute values that matter, but their ratio. If both are increased by the same amount such that the ratio doesn't change, equilibrium doesn't shift at all. However, typically changes are different and the ratio changes as well.
 
  • #6
Borek said:
It is not absolute values that matter, but their ratio. If both are increased by the same amount such that the ratio doesn't change, equilibrium doesn't shift at all. However, typically changes are different and the ratio changes as well.

Got it. Equilibrium can be maintained as long as the ratios are not affected. Thanks for the clarification!
 

Related to Reaction rates, temperature, and thermal energy

What is a reaction rate and how is it measured?

A reaction rate is the speed at which a chemical reaction takes place. It is typically measured by the change in concentration of a reactant or product per unit of time. This can be calculated by dividing the change in concentration by the change in time.

How does temperature affect reaction rates?

Temperature can greatly influence reaction rates. Higher temperatures generally result in faster reaction rates because the particles have more energy and move faster, increasing the likelihood of collisions between reactant molecules.

Why do some reactions require a minimum temperature to occur?

Some reactions require a minimum temperature, known as the activation energy, to occur because they involve breaking and forming chemical bonds. This requires a certain amount of energy to overcome the activation energy barrier and initiate the reaction.

What is thermal energy and how does it relate to reaction rates?

Thermal energy is the energy associated with the motion of particles in a substance. It is directly related to temperature and can affect reaction rates by providing the necessary energy for reactions to occur.

How do catalysts affect reaction rates and temperature?

Catalysts can increase the rate of a chemical reaction by lowering the activation energy required for the reaction to occur. This means that the reaction can occur at lower temperatures, making it more efficient and cost-effective.

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