Rates of Reaction How Fast

Question 1

what do catalysts do

Answer 1

speeds up a reaction but is chemically unchanged at the end of the reaction
provides an alternative route with a lower Ea

Question 2

units for rate

Answer 2

mol dm-3 s-1

Question 3

what is dynamic equilibrium

Answer 3

quantities remain constant, although reactions still continuing- rates of forward and backward reactions equal
Closed system only

Question 4

state Le Chateliers principle

Answer 4

position of equilibrium moves to counteract change

Question 5

how to calculate rate

Answer 5

change in conc/change in time

Question 6

what is first order

Answer 6

rate is proportional to the concentration of A
if you double conc A, rate doubles
rate = k[A]

Question 7

what do [ ] mean

Answer 7

concentration

Question 8

what is second order

Answer 8

rate is proportional to the square of the conc of A
if conc doubles, rate goes up by 4 times
rate= k[A]2

Question 9

what is zero order

Answer 9

if the conc of A changes there is no change on rate

rate= k

Question 10

what is the overall rate of reaction

Answer 10

adding up the individual orders
eg-
rate= k[A]2[B]
order= 3

Question 11

rearrange the rate equation to find k

Answer 11

k= rate/ [A] [B]2

Question 12

k units for

first, second and third order

Answer 12

first- s-1
second- dm3mol-1s-1
third- dm6mol-2s-1

Question 13

what monitoring is concentration-time graphs

Answer 13

continuous monitoring

Question 14

how to find rate of reaction from concentration-time graph

Answer 14

gradient

change in y over change in x

Question 15

what is a zero order conc-time graph like

Answer 15

diagonal
rate of reaction is the same
k=gradient

Question 16

what are the axis of conc time graph

Answer 16

x- time

y- concentration

Question 17

what is a first order conc- time graph like

Answer 17

curved downwards
decreasing gradient over time (slowing down)
half life constant

Question 18

what is a second order conc-time graph like

Answer 18

steeper at start
downwards curve
no constant half life

Question 19

how to calculate k from half life

Answer 19

ln2/half life

Question 20

rate conc graph axis

Answer 20

x- conc

y-rate

Question 21

what is a zero order rate-conc graph like

Answer 21

horizontal line

rate= k

Question 22

what is a first order rate-conc graph like

Answer 22

diagonal line

k= gradient of line

Question 23

what is a second order rate-conc graph like

Answer 23

upward curve

k=plot graph of rate against conc squared and gradient would be k

Question 24

how to find initial rate from conc-time graph

Answer 24

draw tangent at T=0

Question 25

how to find initial rate

Answer 25

1/t

Question 26

limitation of clock reaction

Answer 26

assumes initial rate is constant up to where the measurement is taken

Question 27

what is a rate determining step

Answer 27

slowest step in a multi-step reaction

fast step cant happen until the slow reaction has finished

Question 28

what makes up the Arrhenius Constant

Answer 28

k= rate constant 
Ae= frequency of collisions
Ea= activation energy (joules)
r- gas constant 
t- temperature (kelvin)

Question 29

if there was no activation energy in the Arrhenius Constant what does A tell you

Answer 29

rate

Question 30

log of Arrhenius Constant

Answer 30

ln(k)= -Ea/R x 1/t +ln(A)
y= mx + c (y intercept)

Question 31

rearrange y=mx+ c

Answer 31

c= y-mx