chem 106 quiz 4

Question 1

rule of thumb for temperature and reaction rate

Answer 1

rate constants double for every 10*C increase

Question 2

reaction rate is affected by both ? and ?

Answer 2

concentration and temperature

Question 3

overall, reaction rate is mostly controlled by

Answer 3

activation energy

Question 4

rates increase ? with temperature

Answer 4

exponentially

Question 5

rates depend on 3 things

Answer 5

1. fraction of molecules with KE > Ea
2. collisions/sec
3. orientation (fraction of collisions with correct orientation)

Question 6

Arrhenius Equation

Answer 6

k = A*e^(-Ea/RT)

Question 7

Arrhenius Plot

Answer 7

lnk vs 1/T
slope = -Ea/R
y-intercept is lnA

Question 8

to measure Ea experimentally,

Answer 8

find k at at least two temperatures

slope = -Ea/R on plot of lnk vs 1/T

Question 9

elementary step

Answer 9

one, uninterrupted step

rate law is first order for each reactant

Question 10

multi-step reactions

Answer 10

slow and fast step
intermediate
slow step is rate determining step

Question 11

dynamic equilibrium

Answer 11

rate of forward reaction = rate of backward reaction

Question 12

catalyst

Answer 12

speeds up a reaction by lowering the Ea, changes the mechanism, not consumed in the reaction

Question 13

two kinds of catalysts

Answer 13

homogeneous (same state/phase as reaction) and heterogeneous (diff. phase)

Question 14

catalysts (do/do not) affect overall thermodynamics

Answer 14

do not

enthalpy and equilibrium do not change

Question 15

the equilibrium constant is equal to

Answer 15

k,f / k,r = [product] / [reactant]

Question 16

for gases, Keq = Kp (use ? instead of ?)

Answer 16

pressure; concentration

Question 17

pressure for k is always ?

concentration for k is always ?

Answer 17

atm

M

Question 18

solid concentration doesn’t mean anything, so

Answer 18

exclude it from the calculation of k

Question 19

the concentration of a pure substance (i.e., water) is not changing, so

Answer 19

exclude it from the calculation of k

Question 20

a weak base is expected to have a (small/large) k because

Answer 20

small; won’t dissociate much

Question 21

k will be small for (soluble/insoluble) reactants

Answer 21

insoluble (or not very soluble)

Question 22

how to use ICE

Answer 22

initial
change
equilibrium

should be able to fill in the blanks
initial of products should be zero
use mole ratios (stoichiometric coefficients)

Question 23

reaction quotient (Q) predicts

Answer 23

the direction of reaction

Question 24

if Q = Keq

Answer 24

the reaction is at equilibrium

Question 25

if Q < Keq

Answer 25

the reaction will shift to the right (to make more products, thus increasing Q)

Question 26

if Q > Keq

Answer 26

the reaction will shift to the left (to make more reactants, thus decreasing Q)

Question 27

always check ? when solving for equilibrium pressures

Answer 27

that the Keq values match up

Question 28

if k=1 reaction favors

Answer 28

neither side

Question 29

if k>1 reaction favors

Answer 29

products

Question 30

if k<1 reaction favors

Answer 30

reactants