Reaction Kinetics Flashcards
What is rate of reaction?
Change in concentration of reactant or product per unit time
What is the gradient of concentration-time graph?
rate of reaction
If concentration-time graph is a 1/x² graph, what does this imply?
- gradient decreasing with time
- reaction is slowing down
- rate of reaction is decreasing with time
What is initial rate?
reaction rate at the start of the reaction where an extremely small amount of reactant has been used up
How to obtain initial rate?
determining the gradient of tangent drawn to the curve at time t=0
What is instantaneous rate?
rate of reaction at a particular instant in time
How to obtain instantaneous rate?
gradient of tangent drawn to the curve at that time
What is average rate of a reaction?
Calculated from final change in concentration of reactant or product over a particular period of time
How to obtain average rate of reaction?
Measuring gradient of line drawn between two points on the curve for the time interval
What happens if your calculate rate of reaction is negative?
- rate of reaction always positive
- add a negative sign to make it positive
What is rate equation or rate law?
Experimental relationship between the reaction rate and the concentration of reactants
What is the rate equation of aA + bB → cC + dD
rate of reaction = k[A]ᵐ[B]ⁿ
For rate of reaction = k[A]ᵐ[B]ⁿ, what is k, m, n and m+n?
- k is rate constant
- m is the order of reaction with respect to A
- n is the order of reaction with respect to B
- (m+n) is overall order of reaction
What is order of reaction?
It is the power of the reactant’s concentration term in the experimentally-determined rate equation is the order of reaction with respect to that reactant
What is rate constant, k?
proportionality constant in the experimentally determined rate equation
When is rate constant a constant for a given reaction?
At a given temperature
What affects rate constant, k?
- k increases when temperature increases
- k increases when Ea decreases (using a catalyst)
What is zero-order reaction?
rate of reaction is independent to [reactant]
What does the concentration time graph look like for zero-order reactions? How to interprete the graph?
- downward sloping linear line
- gradient = -k
- gradient is constant which means that rate is constant
What does the rate-concentration graph of zero order reaction look like?
horizontal straight line at k (vertical intercept)
What does the rate-time graph of zero order reaction look like?
horizontal straight line at k (vertical intercept)
What is a first-order reaction?
rate of reaction is directly proportional to [reactant]
What does the concentration time graph look like for first-order reactions?
curve where gradient is getting less steep over time
What is the rate-[concentration] graph of first-order reaction?
- upward sloping linear graph
- gradient = k