rate equations Flashcards
what are in the orders of rate in respect to A
-doubling conc of A then rate is directly prop to A so the rate does not change - order is 1
-doubling A = quadruples rate
(A squared) and order is 2
-doubling A had no effect on rate so order is zero
what is the rate equation
rate = k[A]^m[B]^n
how do scientists find the order of the reactants
through experiments - DO NOT USE BALANCE NUMBERS
what is the rate constant dependent on
temp
how to find overall order
add all orders together
order of a catalyst?
same method as reactants
what are initial rate experiments
conc changed one at a time but everything else remains the same
how to measure rate immediately at the start eg use disappearing cross method
how to find orders using table
start with reactant A - look for two experiments where the conc of A has changed and everything else is the same- then work out order using principles eg if conc of A doubles and rate doubles = first order
then do same for B and then C
then add total orders
OR
work out K
put the values in formula/ rearrange to find which one u are looking for
what to do if cant see relationship easily
divide rate value for bigger conc by smaller
how to rearrange rate equation to find K
k = rate/reactants
what are the units for K
mol^-1 dm^3 s-1
the mol and dm will change
work out using same method as for kc and kp
what does the conc-time graph of a zero order reactant look like
In a zero-order the concentration of the reactant is inversely proportional to time
This means that the concentration of the reactant decreases with increasing time
The graph is a straight line going down
what does the graph for a conc-time graph for first order look like
In a first-order reaction the concentration of the reactant decreases with time
The graph is a curve going downwards and eventually plateau
what does the graph for a conc-time graph for second order look like
In a second-order reaction the concentration of the reactant decreases more steeply with time
The concentration of reactant decreases more with increasing time compared to in a first-order reaction
The graph is a steeper curve going downwards
what is the rate -conc graph for zero order
In a zero-order reaction the rate doesn’t depend on the concentration of the reactant
The rate of the reaction therefore remains constant throughout the reaction
The graph is a horizontal line
The rate equation for this one reactant is rate = k
to find k - to find the gradient - work out from conc-time graph
how to plot a rate-conc graph
The progress of the reaction can be followed by measuring the initial rates of the reaction using various initial concentrations of each reactant
These rates can then be plotted against time in a rate-time graph