1.9 Rate Equations Flashcards
What’s the generalised rate equations for: aA +bB?
What do r, k, n and m stand for?
r is used as a symbol for rate, the unit of r is usually mold-3s-1
k is the rate constant
m,n are reaction orders, which are usually integers.
What do 0,1 and 2 order mean is rate equations?
0 - the reaction is zero order with respect to the reactant
1- 1sr order
2-2nd order
How do you workout the total order for a reaction?
By adding all the individual orders together.
What does zero order mean?
The conc of A has no effect on rate of reaction.
What does the first order mean?
The rate of reaction is directly proportional to the concentration of A
What the second order mean?
The rate of reaction is proportional to the concentration of A squared
What does the units of the rate constant (k) depend on?
The units of k depend on the overall order of reaction. It must be worked out from the rate equation.
What is the value of k independent of?
The value of k is independent of concentration and time. It is constant at a fixed temperature.
What does the value of k refer to?
A specific temperature and it increases if we increase temperature.
What are the units of k for a 1st, 2nd and 3rd order of overall reaction?
When does measurement of the change in volumes of a gas work as a method to track rate of reaction?
If there is a change in the number of moles of gas in the reaction. Using a gas syringe is a common way of following this. It works well for measuring continuous rate but a typical gas syringe only measures 100ml of gas so you don’t want a reaction to produce more than this volume.
Whats a typical method for continuous monitoring through measurement of the change in volume of a gas to find rate?
How can the initial rate be calculated from a graph?
The initial rate can be calculated by taking the gradient of a continuous monitoring conc vs time graph at t=0
