Unit 3.5 Chemical kinetics Flashcards
To be soon
Hopefully no test?
There’s a test coming….
It’s not in order, I have implemented a new method
Sure
… but i like order?
State the rate equation?
Rate = k[A] [B]2
What equation do u get when involving heat with the rate equation?
Arrhenius equation
State Arrhenius equation
K = Ae-Ea/RT
Define K
(Arrhenius equation)
Rate constant
(s-1)
Define A
(Arrhenius equation)
Frequency factor
Define e
(Arrhenius equation)
e from the calculator lol
Define -Ea
(Arrhenius equation)
Activation energy,
although it’s negative
(Jmol-1
Define R
(Arrhenius equation)
Molar gas constant
(JK-1mol-1)
Define T
(Arrhenius equation)
Temperature
(Kelvin aka K)
The “right” Arrhenius equation
In k = In A - Ea/RT
Which has a greater effect on K when changed?
(Arrhenius equation)
(2…)
- Activation energy
- Alternately, so does temperature
What’s the other way to use the Arrhenius equation?
(2….)
- Using the “right” way (log on both sides)
- Expressing it as y = mx + c
How do u plot a graph based on Arrhenius equation?
(2 things)
- In k against 1/T
- used to determine In A and -Ea/R
Arrhenius equation expressed in y=mx+c?
(4 steps)
(Refer to graph…)
(Actually, refer to physics type shi)
- In A =
- y - c = mx
- c = y - mx
- In A = In k - -Ea/R x 1/T
To be continued
.
What are the 5 ways of measuring the rate of reaction?
- Collect gas overtime, measure volume overtime
- Measure loss of mass overtime (mass balance)
- Measure pH change overtime
- Measure the formation of ppt
- Measure color change overtime (colourimetry)
What is “sampling and quenching”?
(2-way + 2-way + “lastly”)
- Small sample of reaction mixture removed
- … at regular time intervals
- (Q) Put into iced water to cool
- (Q) … and diluted, stops the reaction
- Sample then analysed
Rate of a chemical reaction formula?
Rate = change in conc. of (reactants/products)/time for the change to take place
How would u gain the rate of the reaction in a graph typically?
(1 thing + 2-way)
- Differentiate
- Drawing a tangent
- … at point of interest
How to gain units for the rate of reaction?
(3 simple dimple)
- Conc = moldm-3
- Time = min or sec
- Fractional ∴ moldm-3min-1 or moldm-3s-1
How to explain whether it’s greater at “…” mins?
(3-way structure)
- Lots of reactant particles
- Increased frequent collisions
- in contrast to “…”
What is the order of reactions?
(1 + 2-way)
- Always respect to each reactant involved
- Considers how the conc. of reaction….
- affects the rate
What are the 3 orders of reactions?
- Zero order
- First order
- Second order
Zero order shape?
Straight line
Zero order in terms of order of reaction?
(2-way + 2-way)
- Reactant is used up
- Conc. decreases
- But has no effect on rate
- Hence, just a straight line
So, gradient of zero order? Hence the rate?
(2-way + 1 thing)
- Gradient = constant
- so constant rate
- Rate don’t change if conc. changes
What about zero order’s half life?
(2-way)
- Significantly decreases
- as the reaction proceeds
First order shape?
Curve
First order in terms of order of reaction?
Easily identifiable due to constant half life
Define the term “half life”?
(2-way)
- Time taken for the concentration
- to reduce by half
So… first order’s half life?
(2 things)
- Independent of concentration
- Remains constant throughout reaction
Second order shape?
Also curve, but steeper…?
Second order in terms of order of reaction?
(3 things + a surprise)
- Identified from the shape as well
- Conc. decreases more rapidly
- Half life increases with time
- U don’t needa know that apparently
Second order’s half life :v?
(2-way)
- Significantly increases
- as the reaction proceeds
What is the general rate equation?
Rate = k[A]m[B]n
Define rate?
(general rate equation)
moldm-3s-1
(Concentration with the seconds)
Define [A] or [B]?
(general rate equation)
moldm-3
(Their concentration)
Define k?
(general rate equation)
The rate constant
(re-arrange for it)
Define m or n?
(general rate equation)
Powers aka n° infront of compound
(Their order of reaction)
How do u find out a reactions order of reaction?
(4 steps)
- From their rate equation
- Gain their powers
- Add their powers = rate equation
- Power of 1 = doesn’t usually have 1 ofc
How do u find if its zero order with respect to the reactant?
(2-way)
- Rate doesn’t change
- if conc. changes
How do u find if its first order with respect to the reactant?
(3 steppers)
- If conc. increases by 2x
- Rate increases by 2x
- Likewise if 3x too
How do u find if its second order with respect to the reactant?
(6 but trust me)
- If conc. increases by 2x
- Rate increases by 22 = 4x
- If conc. increases by 3x
- Rate increases by 32 = 9x
- Likewise to first order but there’s always
- …. a power of 2
How do u actually gain its rate equation?
(We did it)
(Gain examples)
Refer to its order of reaction
What do u get from finding k (Rate constant) in the rate equation?
(2 things)
- The actual value
- Its units
How do u get the value of k (Rate constant) in rate equation?
(4 steps)
(Whiteboard pls)
- Gain rate
- Gain conc. of compounds
- Re-arrange formula (remember powers)
- Voila
How do u get the units of k (rate constant) from rate equation?
(4 steps)
(Whiteboard pls pls pls)
- Refer to data and units given
- Sub them in, in terms of formula
- Re-arrange
- Voila
Define the term “reaction mechanism”
(3-way)
- Series of steps
- that together make up
- the overall reaction
Define the term “rate-determining step”
(3-way)
- The slowest step
- in the reaction mechanism
- of a multi-step reaction
How to predict the reaction mechanism, from just their rate equation?
(…)
What i’m seeing
- Gain rate equation
- Find the rds (the molecules in the rate equation)
- We don’t know how many steps there are
- But at least we know each step only has 2 molecules involved max
- There’s only 1 rds
- The end of the step is just the overall equation
-… aka the equation we used to find out the general rate equation (kinda)
What is an “intermediate” in the reaction mechanism?
- Species formed in the multi-step reaction
- … used up in a subsequent step
- Not seen as reactant/product of overall equation
Could it be shorter than i think it is?
I think i’ll go wid that, also prob spam ppq way more imp
- Order of reactions ;-;
- General rate equation ;-;
- Rate determining step ;-;-;-;?
- Arrhenius equation (so refer to physics) ;-;?
Ok so, yes. Not a good thing to be too clarifying u know? I hope u learn ur lesson. BUT, don’t give up ofc. The ppq will carry right?
…. <_< ….
We got graph paper fellas. Apparently the questions is the most to be revised on. Content wise…. light work?
