Rate equations Flashcards
Define rate.
Change of concentration of products/reactants per unit time.
What are the units of rate.
mol/dm³
On a conc-time graph, what is the gradient of a tangent equal to?
Rate at that concentration.
What is the rate equation?
rate=k[A]^m [B]^n
What is k?
The rate constant.
How is k measured?
Experimentally.
What does the value of k depend on?
Temperature.
What are the units of k?
Dependent on reaction.
What are m and n?
Order of reaction.
What can the order of reaction be?
»0
»1 (first)
»2 (second)
What is overall order of a reaction?
Sum of all the powers/orders.
What effect does concentration have on rate at 0 order?
No effect.
How is 0 order written?
[X]⁰ - not written.
What effect does concentration have on rate at first order?
Linear effect.
How is first order written?
[X]¹ = [X]
What effect does concentration have on rate at second order?
Quadratic effect.
How is second order written?
[X]²
Describe a rate-concentration graph for 0 order.
Straight horizontal line.
Describe a rate-concentration graph for first order.
Straight positive diagonal line.
Describe a rate-concentration graph for second order.
Curved increasing line.
Describe a concentration-time graph for 0 order.
Straight negative diagonal line.
Describe a concentration-time graph for first order.
Curved decreasing shallow line.
Describe a concentration-time graph for second order.
Curved decreasing steep line.
What happens to rate concentration of temperature increases?
Rate constant increases exponentially.
What is the Arrhenius equation?
k= Ae^(-Ea/RT)
What is A?
Arrhenius constant.
What are the units of A?
Same as k.
What is e?
Euler’s number.
What are the units of e?
No units.
What is Ea?
Activation energy.
What are the units of Ea?
J/mol
What is R?
Gas constant.
What are the units of R?
J/K/mol
What is T?
Temperature.
What are the units of T?
K
What effect does increasing temperature have on rate/k?
Increases rate/k.
What effect does adding a catalyst have on rate/k?
Increases rate/k.
What is the rearranged Arrhenius equation using natural logs?
lnk= (-Ea/RT) + lnA
If graph of Arrhenius equation is drawn, what is y?
lnk
If graph of Arrhenius equation is drawn, what is m?
-Ea/RT
If graph of Arrhenius equation is drawn, what is x?
1/T
If graph of Arrhenius equation is drawn, what is c?
lnA
How can activation energy be worked out from Arrhenius equation graph?
gradient x -R
