Chemical Kinetics: Understanding the Reaction of A & B

In summary, the conversation discusses the calculation of the rate constant and t1/2 for a reaction involving substances A and B. The initial concentration of A decreases by 0.03 M in one hour, and the concentration of B should be 0.05 M. The calculated rate constant is 14.87 l/(mol*h) and the t1/2 for substance A is found to be 1.34 h, which seems unreasonable as more than 50% of the substance reacted in one hour. It is suggested that the simple relation between rate constant and t1/2 may only apply when the concentrations of A and B are equal. A solution is found where t1/2 for A is 0.756
  • #1
krootox217
51
2

Homework Statement


The task is the following:
e6rlc6W.jpg


If the concentration of A decreases 0.03 M in one hour, then the concentration of B should to, which means, [ B] should be 0.05 M?

And if I try to calculate k, i get 14.87 l/(mol*h)

For second order reactions, t1/2 sould be 1/(k*[A]0)

So I get 1.34 h as t1/2 for substance A, which somehow doesn't make sence, since more than 50% of the substance reacted in one hour. For B i get 9.29h, which doesn't make sense too. Can me someone tell my mistake?

Homework Equations


see above

The Attempt at a Solution


see above
 
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  • #2
krootox217 said:

Homework Statement


The task is the following:
e6rlc6W.jpg


If the concentration of A decreases 0.03 M in one hour, then the concentration of B should to, which means, [ B] should be 0.05 M?

And if I try to calculate k, i get 14.87 l/(mol*h)

For second order reactions, t1/2 sould be 1/(k*[A]0)

So I get 1.34 h as t1/2 for substance A, which somehow doesn't make sence, since more than 50% of the substance reacted in one hour. For B i get 9.29h, which doesn't make sense too. Can me someone tell my mistake?

Homework Equations


see above

The Attempt at a Solution


see above

If the concentration of A decreases 0.03 M in one hour, then the concentration of B should to, which means, [ B] should be 0.05 M? YES

I calculated the same rate constant as you.

Always good to check for reasonableness.

However I think that the simple relation of rate constant to half life only applies for the case of equal concentrations [A] = [ B]. ?

I am not sure there is any useful simple relation like that when these two are not equal. So I think you will have to work out each case using the full integrated rate equation, e.g. With [A]/[A0] = ½ and [ B] = [ B0] - [A0]/2 etc.
 
  • #3
Ok, thanks for the answer, I found a way, where t1/2 for A yields 0.756h, which seems to make sence, at least for this reaction :)
 

FAQ: Chemical Kinetics: Understanding the Reaction of A & B

1. What is chemical kinetics and why is it important?

Chemical kinetics is the study of the rates of chemical reactions and the factors that influence them. It is important because it helps us understand how fast a reaction will occur and allows us to control and optimize reactions in industrial processes and in living systems.

2. How does the reaction of A & B work?

The reaction of A & B involves the collision of molecules of A and B, which then form new products. The reaction rate is determined by the concentrations of A and B, as well as the temperature, presence of a catalyst, and other factors that affect the collision frequency and the energy of collisions.

3. What is the difference between reaction rate and rate constant?

Reaction rate is the speed at which reactants are consumed or products are formed in a chemical reaction, while rate constant is a proportionality constant that relates the reaction rate to the concentrations of the reactants. Rate constant is specific to a particular reaction at a given temperature, while reaction rate can vary depending on the concentrations of reactants.

4. How do temperature and concentration affect the rate of a reaction?

Increasing temperature generally increases the rate of a reaction, as it provides more kinetic energy for the molecules to collide and overcome the activation energy barrier. Increasing the concentration of reactants also increases the rate of a reaction, as it increases the frequency of collisions between reactant molecules.

5. What is a catalyst and how does it influence the reaction of A & B?

A catalyst is a substance that increases the rate of a reaction without being consumed in the reaction itself. It works by lowering the activation energy required for the reaction, making it easier for the reactant molecules to collide and form products. In the reaction of A & B, a catalyst can increase the rate of the reaction by providing an alternative pathway with a lower activation energy.

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