How fast?

Question 1

What is the rate of reaction?

Answer 1

Change in concentration/ change in time

Question 2

What is rate of reaction proportional to?

Answer 2

The concentration of a particular reactant raised to a power

Rate ∝ [A]^n

Question 3

If the concentration of a reactant is raised to the power n, what is n?

Answer 3

The order of the reaction

Question 4

What is zero order?

Answer 4

When the concentration of a reactant has no effect on the rate. Rate ∝ [A]^0.

Concentration has no effect on the rate for zero order because any number raised to 0 equal 1

Question 5

What is first order?

Answer 5

when the rate depends on its concentration raised to the power 1 - rate ∝ [A]^1

• If the concentration of A is doubled, the reaction rate increases by a factor of 2^1
• If the concentration of A is tripled, the reaction rate increases by a factor of 3^1 = 3

Question 6

What is second order?

Answer 6

When the rate depends on its concentrations raised to the power 2 (squared) - rate ∝ [A]^2

• If the concentration of A is doubled, the reaction rate increases by a factor of 2^2 = 4
• If the concentration of A is tripled, the reaction rate increases by a factor of 3^2 = 9

Question 7

What is the overall order?

Answer 7

The sum of the orders with respect to each reactant - it gives the overall effect of the concentrations of all the reactants on the rate of reaction

Question 8

What is the rate constant?

Answer 8

The proportionality constant; its a constant value that converts between the rate of reaction and concentration of orders

Question 9

What is half-life?

Answer 9

The time taken for half of a reactant to be used up

Question 10

What is the rate-determining step?

Answer 10

The slowest data in a multi-step reaction

Question 11

How do you find the orders of reactants when given the rates?

Answer 11

Compare 2 experiments, with one of the reactants concentrations staying the same and the others changing - analyse what effect this have on the rate

Question 12

What is the rate equation?

Answer 12

rate = k[A]^m[B]^n

k = rate constant
[A] = concentration of A
m = order of A

Question 13

How can you calculate the rate constant?

Answer 13

k = rate/ [A]^m[B]^n

Question 14

Whats the units of the rate constant if the overall order is 0?

Answer 14

mol dm^-3 s^-1
k = rate

Question 15

Whats the unit of rate constant if the overall order is 1?

Answer 15

s^-1

Question 16

What is the unit of the rate constant if the overall order is 2?

Answer 16

mol^-1 dm^3 s^-1

Question 17

What is the concentration time graph for a zero order reaction?

Answer 17

Question 18

What is the concentration-time graph for a first order reaction?

Answer 18

Question 19

What is the concentration-time graph for a second order reaction?

Answer 19

Question 20

What is the gradient of a concentration-time graph equal to?

Answer 20

The rate of reaction

Question 21

How can you calculate the rate constant from a concentration-time graph?

Answer 21

• Pick a point on the graph of a specific reaction
• Draw a tangent to the line at this point
• Calculate the gradient of the tangent
• k = rate/ [A] : rate = gradient and [A] is the concentration at the chosen point

Question 22

How can a first order relationship be confirmed from a conecentration-time graph?

Answer 22

Measuring successive half-lives - if they are the same the reaction is first order with respect to the reactant. Measure at-least 3 to check!

Question 23

What is the rate constant equation for a first order reaction?

Answer 23

k = ln 2 / t 1/2

k = rate constant
t 1/2 = half life

Question 24

What is the rate-concentration graph for a zero order reaction?

Answer 24

Question 25

What is the rate-concentration graph for a for a first order reaction?

Answer 25

Question 26

What is the rate-concentration graph for a second order reaction?

Answer 26

Question 27

How do you investigate initial rates using iodine clocks?

Answer 27

Question 28

How do you investigate reaction rates using continuous monitoring of Mg and HCl?

Answer 28

• For each HCl concentration, plot a graph of time on the x-axis against volume of H2 gas produced on the x-axis
• Draw a line of best fit
• Draw a tangent at time = 0s. Use the gradient to the initial rate for each concentration HCl

Question 29

How do you investigate rates by analysing colorimetry?

Answer 29

Question 30

What does the rate equation include?

Answer 30

It only includes repeating species involved in the rate-determining step

The orders in the rate equation match the number of species involved

Question 31

If (CH3)3 CBr + OH- —> (CH3)3COH + Br-
and the rate equation is rate = k[(CH3)3CBr]
what does this show?

Answer 31

The slow rate-determining step involves only one molecule of (CH3)3CBr

OH- has no effect on the reaction rate and must be involved in the fast step

Question 32

What happens to the rate of reaction and rate constant as the temperature increases?

Answer 32

The rate of reaction and rate constant will also increase

Question 33

What 2 factors contribute to the increase of rate of reaction and rate constant with temperature?

Answer 33

• Increasing temperature shifts the Boltzmann distribution to the right, increasing the proportion of particles that exceed the activation energy
• As temperature increases, particles move faster and collide more frequently

Question 34

What is Arrhenius’ equation?

Answer 34

k = Ae^- Ea/ RT

k = rate constant
A = Arrhenius constant
Ea = activation energy
R = gas constant
T = temperature K

Question 35

How can Arrhenius’ equation be expressed as a logarithmic relationship?

Answer 35

ln k = - Ea/ RT + ln A

Question 36

If you plotted a graph of ln k against 1/T, what is the gradient and y-intercept?

Answer 36

gradient = -Ea/ R
y - intercept = ln A