Unit 4.1 kinetics Flashcards
inert gas
gas that does not react with other substances bc it is stable so no chemical reactions
ex- helium, argon
what happens if an inert gas is added to a reaction?
nothing lol
adding an inert gas does not affect the rate or equilibrium yes or no
ya adding an inert gas does not affect the rate or equilibrium bc it doesn’t participate in reaction stuff
catalysts
increases the rate of a chemical reaction without being consumed.
also lowers activation energy obviously
and allows for more successful collisions
what are the 3 types of catalysts
biological catalysts, homogeneous catalysts, heterogeneous catalysts
biological catalysts
enzymes are special proteins that are specific to substrates like they do this in humans and plants
homogeneous catalysts
-they stay in the same phase (state) as the reactants
-they work bc theyre in the same phase and can mix easily with reactants which make the reactions happen faster
like putting more water in batter to make it more flowy and easier to stir
heterogeneous catalysts
-catalysts in a different phase form the reactants.
-catalysts and solid, reactants are liquid or gas
-they work by the reactants coming in contact with the catalyst and speeds it up but they never mix together
like how rocks help a river flow faster
temp and reaction rate rule of thumb
10 degrees celcius increase will double the reaction rate
collision theory
-a reaction happens when particles collide with enough energy (activation energy) and the correct orientation
-increasing the concentration of reactants or raising the temperature increases collision rates, this increasing the reaction rate
-more frequent or energetic collisions lead to faster reactions
how does a catalyst affect the rate of a chemical reaction?
it lowers the activation energy, leading to a more successful collisions and faster reaction rate
what energy do particles need to collide
transitional energy (their movement) to convert vibrational energy to bond together so they hit hard enough they stick together
when collisions meet all their criteria to bond thats called
effective collisions
criteria for effective collisions
-enough energy
-correct orientation
activation complex
after particles collide with enough energy, they form activated complex which is like the highest energy point (peak of the curve)
at this state they can continue and form products or fall back to original reactants
reaction rate formula
rate= change in concentration / time interval
rate=M/sec
is the rate constant
no
instantaneous reaction rate
finding the rate at a specific time
how to find instantaneous reaction rate
1) draw a tangent line at the point on the graph youre interested in
2) find the y-int and thats the M
3) find the x int where the line ends and thats sec
4) then do M/sec
5)units are Ms^-1
what is relative reaction rate
the rate at which reactants disappear or products appear in a reaction
relative reaction rate for a reactant
rate is always negative since its disappearing
relative reaction rate for a product
rate is always positive since its forming
relative reaction rate formulas
ex- 2NO2–> O2 + 2NO
divide each coefficient into a fraction and make reactants neg and products pos
and put each one equal to each other and divided by triangle t
-1/2 ▲[NO2] / ▲ t = ▲[O2]/▲t =
1/2 ▲[NO] /▲t
what is the rate constant
K, it tells us how fast the reaction goes
reaction order: zero order
rate= k
changing the amount of this reactant doesn’t change the reaction speed
reaction order: first order
rate= k[A]
if you double the amount of this reactant the reaction goes twice as fast
reaction order: second order
rate: k[A]²
if you double the reactant the reaction goes four times as fast (bc its squared)
overall order
add up the order number of each reactant
kinetics
the study of how fast a reaction happens (rate) under different conditions
thermodynamics
tells us if a reaction is possible, but kinetics tells us how fast it will happen
factors that affect reaction rates: nature of reactants
1) physical state: solids react slower than liquids or gases bc slower
2) chemical identity: some react faster than others like
- when there molecules with opposite charges
- it has fewer bonds so breaks apart easy
factors that affect reaction rates: concentration of reactants
higher concentration= faster reaction bc more molecules are available to collide
factors that affect reaction rates: temperate
higher temp= faster reaction rate
bc move faster, more frequent collisions
factors that affect reaction rates: surface area of reactants
more surface area= faster reaction
bc more particles are exposed to collide
additional factors affecting rate: inert gas
inert gas does not affect gas
successful collision energy:
-must have enough energy to overcome the bonds in the reactants
-allows them to break out ones and create new ones=reaction
differential rate law
this is used when we have concentration and rate data.
it tells us the rate of the reaction based on concentration
integrated rate law
this is used when we have concentration and time (like how much is left after 10 mins, 20 mins)
helps us figure out how long it takes for a reactant to disappear
how do you plot integrated rate law
use natural log of the concentration (ln)
you’re given 3 graphs and u wanna know which one is zero order
its the graph that has the straightest line vertically and is negative
also, the graph is labeled y axis concentration x axis time
first order graph
negative slope
the graph is labeled y axis natural log of concentration x axis time
second order graph
positive slope
y axis concentration ⁻¹ (reciprocal) and x axis time
what does [A] mean
concentration
what does [A]₀ mean
starting concentration
integrated rate law: zero order
[A]= -kt + [A₀]
integrated rate law: first order
ln[A]= –kt + ln[A₀]
integrated rate law: second order
1/[A] = kt + 1/[A₀]
what does k mean
the rate constant
even thought the second order graph line is positive…
the concentration is decreasing but since its the reciprocal (the opposite) its graphed positive
