Unit 6- Kinetics Flashcards
_____ catalyze most reactions that take place in the body.
Enzymes
Why are we interested in the rates of reactions?
The rates of the reaction can be used to help determine the mechanism of a reaction, and catalysts allow us to carry out reactions in a more efficient manner.
What does the “mechanism” of a reaction mean?
In detailed explanation of how the reactants and catalysts interact to form the product.
What do catalysts do specifically?
They lower the activation energy of a reaction.
How is a reaction rate illustrated on a graph?
Curves are constructed for the concentration of the reactant and the concentration of the product through the progression of time. The concentrations are obtained from a spectrophotometer and to use the spectrophotometer titrations need to be done.
The change in the concentrations of the reactants is highest when and lowest when?
Highest near the beginning and lowest near the end of the reaction.
What is a rate expression? what is the basis of it?
General formula for rate determinations
The basis of it is that it is 1 over the moles of reactant times the negative change in concentration of the reactant over time is equivalent to 1 over the moles of product times the + change in concentration of products.
Define Rate Laws
They are solely based on the concentration of the reactants.
What is the difference between rate laws and rate expressions?
Expressions can be written using both the products and the reactants whereas rate laws can be written only using the concentration of the reactants.
How does the increase in the concentration of reactants affect the rate?
With an increased concentration of reactants, the rate will increase (more frequent collisions)
_____ are the exponents on the reactants and are determined experimentally.
Rate Orders
Why does the initial rate of the reaction provide useful information about how reactants interact in the reaction?
Because the reactants are at high concentration, which means that more frequent collisions are happening. So, from this, we can determine the mechanism of the reaction.
What information do reaction orders provide us with?
They provide information for how the reactants behave.
Define Transition State
The configuring of atoms act maximum in the potential energy profile.
What is the value of the rate constant dependent on?
The temperature and the addition of a catalyst; IT IS NOT DEPENDENT ON THE CONCENTRATION OF REACTANTS.
If constant temperature and no catalyst; _____ doesn’t affect k.
Increase in the concentration of reactants.
How do you speed up a chemical reaction?
Increasing the temperature leads to the increase in kinetic energy of the molecules, leading to more frequent collisions. So, molecules can reach activation energy. Increasing the concentration of the reactants. Using catalysts to lower the activation energy.
Substrates are _____.
Reactants
Explain everything about zero order reactions.
The concentration of the reactant does not have an impact on the rate. There is a negative slope on a plot of [] over the course of time.
Explain everything about 1st-order reactions
They have a negative slope on a graph with the plot of ln[] over the course of time. The half life of a first order reaction is the .693/k
Explain everything about 2nd-order reactions
They have a positive slope for the plot of 1/[] over the course of time. The half life for the second order reaction is 1/k[A]0
What is the Collision Theory
As the average kinetic energy increases, the average molecular speed increases, and thus the rates of collisions increases.
What was done for the in-class activity?
Used the absorbance + concentration at time 0 to find the molar absorbpivity; then the epsilon and the absorbance value were used to find the concentration at a certain time. Then, ln [] or 1/[] was plotted.
How do we know if the reaction is of a certain order based off of the graphs obtained?
Whichever one has a greater R^2 value corresponds to the one that it is supposed to match.
