module 5 (p1)

Question 1

what does zero order mean

Answer 1

conc of reactant doesn’t affect the rate

Question 2

what does first order mean

Answer 2

conc of reactant affects the rate raised by power of 1

Question 3

what does second order mean

Answer 3

conc of reactants affects the rate raised by power of 2

Question 4

give the equation for the rate constant

Answer 4

rate = k [A]

Question 5

how are concentration-time graphs made

Answer 5

plotting using continuous measurements during course of reaction

(continuous monitoring)

Question 6

how is the gradient of the zero order on a C-T graph different from the other orders

Answer 6

straight line with a downward gradient

Question 7

what is the half life

Answer 7

time taken from half a reactant to be used up

Question 8

what does a first order have in terms on half life

Answer 8

exponential decay

the concentration of reactant halves at a constant time

Question 9

how do we calculate k using a CT graph using the rate

Answer 9

1. calculate gradient of tangent
2. position where tangent has been in the conc. of the reactant
3. rearrange the equation r = k [A]

Question 10

how do we calculate k using a CT graph using the half life

Answer 10

k = ln2 / half-life

Question 11

what is the gradient of zero order in a rate-concentration graph

Answer 11

no gradient (horizontal)

Question 12

what is the gradient of first order in a rate-concentration graph

Answer 12

straight line gradient from the origin

Question 13

how do we calculate k in zero order R-C graph

Answer 13

the y-intercept

Question 14

how do we calculate k in first order R-C graph

Answer 14

(rate is directly proportional to conc.)

k is determined by measuring the gradient

Question 15

how do we calculate k in second order R-C graph

Answer 15

plotting a second graph with conc^2 to give a straight line graph

gradient = k

Question 16

describe a clock reaction

Answer 16

the time at the start of experiment measured for visual change

Question 17

what does a clock reaction assume

Answer 17

average rate of r. is the same as the initial rate

initial rate directly proportional to 1/time

Question 18

define a reaction mechanism

Answer 18

series of steps that make up an overall reaction

Question 19

what is the rate-determining step

Answer 19

the slowest step

Question 20

what does the orders in rate equaton show

Answer 20

number of species involved in the R-D step

Question 21

CH3Br is hydrolysed with a hot aqueous alkali.

r = k [CH3Br]

what is the overall equation and what are the steps?

Answer 21

1) CH3Br –> CH3+ + Br-

2) CH3+ + OH- –> CH3OH

overall) CH3Br + OH- –> CH3OH + Br-

Question 22

describe the factors affecting the rate constant

Answer 22

increasing temperature shifts the boltzmann distribution to the right, higher proportion of molecules that exceed activation energy

(change in rate mostly determined by this)

particles move faster so they collide more frequently

Question 23

what is the arrhenius equation

Answer 23

k = A e^-Ea/RT

Question 24

what is the arrhenius equation in logarithmic form

Answer 24

lnk = -Ea/RT + lnA

Question 25

how do you plot the arrhenius equation in logarithmic form graphically

Answer 25

plot lnK over 1/T

gradient = -Ea/R

lnA = y-intercept