Chem 112B Exam 4 Flashcards
A single-step reaction is called an __________ reaction
elementary
How to find rate law of a table?
Compare the rates of 1-2 experiments to see if rates doubled or halved. The exponent 2 would be on a rate that doubled.
We can directly derive rate laws of elementary reactions from _________
stoichiometric coefficients
Intermediates
are produced in an early step and consumed in a later step
DO NOT appear in the overall reaction or rate law
Rate-determining step of a multi-step reaction
Slowest step (Largest activate energy Ea)
Integrated rate laws describe
the reactant concentration as a function of time
0th reaction order integrated rate law
Law: [A]t= -kt +[A]0
Linear Plot: [A]t vs. t
Slope: -k
Units of k: M/s
1st reaction order integrated rate law
Law: ln([A]t)= -kt +ln([A]0)
Linear Plot: ln([A]t) vs. t
Slope: -k
Units of k:s^-1
2nd reaction order integrated rate law
Law:1/[A]t =kt + 1/[A]0
Linear Plot: 1/[A]t vs. t
Slope: k
Units of k:M-1s-1
Half-life remains constant for
1st order reactions
Half life increases over time for
second order reactions
4 factors that affect reaction rates
1) Concentrations/partial pressures of reactants
2)Physical state (phase)
3)Temperature
4)Catalyst presence
Catalysts speed up reactions by
lowering activation energy
Catalysts do not affect
thermodynamic values like H and E
Catalysts can
appear in the rate law and change the reaction mechanism
Catalysts cannot
appear in the overall reaction
The active site for an enzyme is based on
shape, size, and chemical properties
To find a catalyst,
species if consumed on reactants side then reproduced
Phosphorylation
The addition of a phosphoryl group onto a chemical structure
Which functional groups are most commonly phosphorylated?
Alcohols or amines in amino side chains
Phosphorylation will completely change
the shape of a protein, which causes a new function (turn on/off, enzyme location)
ATP provides ____________ in phosphorylation reactions
the phosphoryl group
Enzyme catalysis requires
enzyme-substrate binding
kcat
Rate constant for the conversion of the enzyme/substrate complex to product
Large kcat
Faster conversion of complex to products
Small kcat
Slower conversion of complex to products
Km tells us
how tightly enzymes bind
Large kM
Takes more substrate to reach 1/2 Vmax
To maximize catalytic efficiency, we want
large kcat and small kM
Chemical equilibrium factors
Concentrations of reactants/products are equal
Rates of forward and reverse reactions are =
Chemical equilibrium can be reached…
from either direction
Equilibrium constant is a
unitless value (Keq)
Kc is expressed using
molarity (concentration)
Kp is expressed using
partial pressures
What does not appear in the equilibrum (Keq) expression?
Liquids and solids
Keq=
Kc = Kp = products/reactants
In the Kp = Kc (RT)^n equation, what is R?
0.08206 Latmmol-1*K-1
When delta n =0,
Kp=Kc
molarity=
moles/liters
Keq»_space; 1
Products dominate, forward favored
Keq = 1
equilibrium
Keq «_space;1
Reactants dominate, reverse favored
When a reaction is multiplied by a number
Raise keq to the power of that number
When a reaction is reversed
Keq is the inverse of Keq for the forward reaction
If a net reaction is the addition of multiple steps
Keq is the product of the Keq values of the individual steps
Q < Keq
Too many reactants, so proceed right/forward