Reaction Rates Flashcards
(20 cards)
What is a rate of reaction defined as?
A change in the amount of reactant or product per unit time, or how fast a reaction progresses over time. It is a positive value.
What is rate of appearance?
The products being created and their concentration (partial pressure) will increase over time. This is the rate of production of how fast products are formed over time, it is also a positive value.
What is rate of disappearance?
The reactants are being used up, so their concentration (partial pressure) will decrease over time. This is basically rate of consumption, it is a negative value
What is an instantaneous rate?
Occurs at a specific time point, slope at one point in time (slope of the tangent line)
What is initial rate?
A type of instantaneous rate, takes place at t = 0 and is the slope of the tangent line at t = 0
What is average rate?
Slope of a line connecting two time points
How can we determine the rate law of a reaction?
1.) method of initial rates (multiple experiments, changes concentration of one reactant only, determine effect of concentration on rate)
2.) integrated rate laws (single experiment, measure concentration at different times, plot 3 curves)
What is differential rate law?
Rate of reaction depends on concentrations
What is integrated rate law?
The concentration of species in the reaction depend on time
What is a half life?
Time required for the concentration to decrease by 50% of the initial concentration
What is the highest energy state?
The transition state (the highest peak of the reaction)
What is a activated complex?
A high energy short lived complex where the molecular configuration is somewhere between the reactants and products (shows bonds being formed and broken)
What does the Arrhenius equation show?
How activation energy, temperature, and rate are related
How does temperature impact rate of reaction?
Increasing temperature means molecules have more energy, have a larger value for k, and have an increased reaction rate
How does activation energy impact rate of reaction?
A lower activation energy leads to more molecules able to react, and therefore increased reaction rate. There is also a larger value for k.
What is the rate determining step?
The rate of the mechanism cannot be faster than the rate of its slowest step (like having a larger activation energy)
What is a catalyst?
- Not a reactant or product
- You have to start with it and end with it (but it is not seen in the overall reaction)
- Catalyst will not affect a reaction mechanism
- Will be consumed by one elementary step and then reformed by a subsequent step
How does a catalyst affect a reaction energy diagram?
- Lowers activation energy
- Changes number of steps in the mechanism
What is a homogenous catalyst?
They are in the same phase as the reactants, are also usually liquids or gasses.
What is a heterogeneous catalyst?
Usually solids that facilitate a reaction by absorbing the reactants onto their surface
