Kinetics Flashcards
What is the reaction rate?
The speed of a chemical reaction, used to measure how fast the reaction make products or uses reactants
What is rate?
How much a quantity changes in a given period of time
What is the average rate?
The change in measured concentrations over any particular time period
What is the instantaneous rate?
The change in [] over one specific time period
What are three common techniques used to monitor a reaction mixture?
Polarimetry, spectroscopy, and pressure measurement
What is rate law?
An equation relating concentration of reactants to rate when the reverse reaction is negligible
What is the order of the reaction?
The sum of the exponents on the reactants
If a reaction is zero order…
Doubling [a] will have no effect on the reaction rate
If a reaction is 1st order…
Doubling [a] will double the rate of the reaction, therefore it is directly proportional to the reactant [].
If a reaction is 2nd order…
Doubling [a] will quadruple the rate of the reaction because rate is directly proportional to the square of the reactant concentration
For a particular reaction in which A → products, a doubling of the concentration of A causes the reaction rate to double. What is the order of the reaction?
1st order
For a reaction
rate = k[A]m[B]n
what will the overall order be?
m+n
What are the units referring to each one of the reaction orders?
zero order = M/s
first order = 1/s or s-1
second order = 1/M.s or M-1s-1
In a forward reaction the concentration of the reactants is ___________ and of the products is ____________
Decreasing, increasing
In a graph of [] over time, the rate can be determined if ___________ by applying the ____________ of ___.
The [] of a substance is known at two distinct points in the reaction, by applying the slope formula of delta y/delta x.
The average rate is the more time specific one.
False, it is the instantaneous rate.
Reaction rate can be determined by the balanced reaction alone.
False, it cannot be determined by the balanced chemical equation alone.
What is the rate formula of a reaction?
Rate = k[A]m[B]n
Which formula can be used to solve for the constant “k”?
k = rate/[A]m
What is the integrated rate law?
It’s what identifies the relationship of the [] reactants vs time
What is the half-life of a reaction?
It is the time required for the concentration of a reactant to fall to 1/2 of its initial value.
What if the reaction mechanism?
A series of individual chemical steps by which an overall chemical reaction occurs.
At the beginning of the reaction, the [] of the product is always:
Zero
The rate of a a chemical reaction speeds up as the reactants form products.
False, it slows down
The rate law is determine by the coefficients of the balanced equation
False
If the units of “k” were M/s, we are able to determine that the reaction is:
Zero order
If the units of “k” were 1/M s, we would be able to determine that the reaction is:
Second order
If we collect concentration and rate data that shows the rate remains the same with concentration changes, we can determine that the reaction is:
Zero order
How do you selected which integrated rate law equation to use?
It is based upon the reaction order
What is the general concept of Kinetics?
rate = -Δ[reactant]/ΔT = Δ[product]/ΔT
For a particular reaction in which A → products, a doubling of the concentration of A causes the reaction rate to double. What is the order of the reaction?
1st order
What does the slope (or curve) indicate in an integrated rate law graph?
The rate order
How can we define dynamic equilibrium?
The rates of the forward and reverse reactions are equal and opposite
Once equilibrium is stablished, the [] of the reactant and products double.
False, once they reach equilibrium the [] does not change
What does it mean if K >> 1?
That the reaction favors product formation at equilibrium
What does it mean if K << 1
That the reaction favors reactant formation at equilibrium
What does it mean if K = 1?
That the neither product is favored at equilibrium and reaction proceeds to midway point
What is the term for when rates of the forward and reverse reactions occur at the same rate?
Dynamic equilibrium
K is not the result of the concentrations of the reactants and the products.
False, K is the result of the concentrations of the reactants and the products.
The _________ of a reaction is the time required for the concentration of a reactant to fall to 1/2 of its initial value
Half-life
What is the series of individual chemical steps by which an overall chemical reaction occurs?
Reaction Mechanism
What is an elementary step?
A step that cannot be broken down into simpler steps
What are the two requirements for a reaction mechanism?
The steps must sum to the overall reaction and the mechanism must predict an experimentally observed rate law
What are molecules that can be canceled in a reaction mechanism?
Reaction intermeadiates (similar to spectator ions)
The rate determining step is much faster than the others.
False, it is much slower than the others
What is the reactio quotient (Qc)?
The ratio at any point in the reaction of the [] of the products raised to their stoichiometric coefficients divided by the [] of the reactants raised to their stoichiometric coefficients.
What happens if Q < K?
The reaction goes to the right, towards the products
What happens if Q> K?
The reaction goes to the left, towards the reactants
What happens if Q = K?
The reaction is at equilibrium
If your reaction reads:
2CO(g) CO2(g) + C(s)
What will your equilibrium equation be?
K = [CO2]/[CO]2
Because solids are not included in this type of reaction
If your reaction reads:
CO2 (g) + H2O (l) H+(aq) + HCO3-(aq)
What will the equilibrium constant be?
K = [H+][HCO3-]/[CO2]
This is straight forward. What types of substances would not be included in writing an equilibrium constant expression?
Solids and liquids
When the reaction is reversed, the new K is the _____ of the original.
Inverse
When the reaction is mulitiplied by a factor, the new K is the “original K” rasied to the power of the factor.
true
When is it more likely for the x is small rule to be applied?
The x is small approximation is most likely to apply to a reaction with a small equilibrium constant and an initial concentration of reactant that is not too small
Kc’s unit is grams
False, Kc is unitless but based upon concentration, is is measured in M
