Rate equation
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Temperature affecting the rate constant? (k)
Rate constant fixed at a fixed temperature. If temps increases then so does the rate constant.
Temperature affecting the concentration of substances? Implications on the rate constant? (k)
Conc of substances remain constant so k must change
Unit rules for calculating order of reaction
s-1 always on the top 1 moldm-3 on the top Number of substances on the bottom as each representing 1 moldm-3 Units only change if calculating for k - if not it is always moldm-3
Steps in calculating rate constant
Write rate expression Re-arrange to make k the subject Solve with given values
What does zero order look like in a concentration-time graph and a rate-concentration graph
Time: Straight diagonal line from high to low Rate: Horizontal straight line high on the graph
What does first order look like in a concentration-time graph and a rate-concentration graph
Time: Curved line from high to low Rate: Straight diagnol line from low (origin) to high
What does second order look like in a concentration-time graph and a rate-concentration graph
Time: Highly curved line from high to low Rate: Curved line from low (origin) to high
What is the rate determing step?
The slowest rate step which depends the whole rate of the reaction
Which factors could spped the rate determing step?
Using a catalyst Altering temperature
How to determine if an equation is the rate determining step?
If all of the rate equation is present in the step. Also if another step can be substitituted in to make all the rate equation present.
What are the two forms of the arrhenius equation?
K = Ae^-(Ea/RT) ln K = ln A - (Ea / RT)
What arrhenius equation is used when determing activation energy for a reaction?
ln K = ln A - (Ea / RT)
What arrhenius equation is used when determing rate constant at 2 different temperatures for a reaction?
K = Ae^-(Ea/RT)
What arrhenius equation is used when determing rate constant with and without a catalyst for a reaction?
K = Ae^-(Ea/RT)
Rearrange the arrhenius equation for Ea
Ea = RT(ln A - ln K)
Rearrange the arrhenius equation for A
A = ke^(Ea/RT)
Rearrange the arrhenius equation for T
T = Ea / R(ln A - ln k)
When using arrhenius for calculating between 2 temps and for with and without a catalyst - what are the units for Ea and temp?
Ea - J so x1000 T - K so +273
What is the equation for graphical analysis of the arrhenius equation? Where is each component found on the graph?
ln k = -(Ea/RT) + ln A ln k = y axis y intercept = ln A gradient = -(Ea/RT)
The rate equation for a reaction is: rate = k[E] Explain qualitatively why doubling the temperature has a much greater effect on the rate of the reaction than doubling the concentration of E. [3]
[1] Reaction occurs when molecules have E>Ea [2] Doubling T by 10 °C causes many more molecules to have this E [3] Whereas doubling [E] only doubles the number with this E