5.1.1 - How fast

Question 1

Define rate of reaction

Answer 1

Change in concentration of a reactant or a product per unit of time

Question 2

At a given instant, how could you calculate the rate of reaction?

Answer 2

Rate of reaction = Change in concentration / time

Question 3

If the order is zero with respect to a reactant, what does that mean?

Answer 3

Changing the concentration of the reactant has no effect on the rate

Question 4

What is the effect on rate in a first order reaction?

Answer 4

Rate is directly proportional to the concentration

Question 5

What is the effect on rate in a second order reaction?

Answer 5

Change in rate = Change in concentration squared

Question 6

Write a generic rate equation and state what each term means

Answer 6

Rate = K [X]ˣ [Y]ʸ
k = rate constant for the reaction
[X] and [Y] are concentrations of species X and. Y and x and y are the orders of reaction with respect to X and Y

Question 7

Do zero order reactants. appear on rate equation? Why?

Answer 7

No, because they don’t have an effect on the rate

Question 8

How is overall order of a reaction. calculated?

Answer 8

Sum of individual orders

Question 9

How would you calculate the units of the rate constant?

Answer 9

rearrange for k and cancel out units to get resultant

Question 10

When the overall order is 3 what would be the units for rate constant?

Answer 10

dm^6mol^-2s^-1

Question 11

How could. you measure the rate of reaction experimentally?

Answer 11

Use a colorimeter at suitable. intervals if there is a colour change
if gas is evolved, use. a gas syringe to collect volume of gas. evolved, or measure the change in mass of the reaction. mixture

Question 12

What does half life mean?

Answer 12

The time taken for concentration of a reactant to decrease. by half

Question 13

What is the symbol for half life

Answer 13

t₀.₅

Question 14

What is the relationship between first order reactions and half life?

Answer 14

First order reactions have constant half lifes

Question 15

What is the equation that is used to determine rate constant using half life in a first order reaction?

Answer 15

K = ln(2) / t₀.₅

Question 16

What is the relationship between rate and time?

Answer 16

rate proportional to 1/t

Question 17

How to determine the rate constant from a rate concentration graph of first order?

Answer 17

k = rate / concentration

Question 18

What is the rate determining step?

Answer 18

The slowest step in a reaction with multiple steps

Question 19

How does the rate determining step link to the species involved in the rate equation?

Answer 19

Any species involved in the rate determining step appear in the rate equation.
Species only involved after the rate determining step do not appear in the rate equation

Question 20

For a reactant in the rate equation, what indicates how many molecules of that reactant are involved in the rate determining step?

Answer 20

The order of reactant

Question 21

What affects the value of the rate constant for a given reaction?

Answer 21

Temperature, nothing else

Question 22

What is the Arrhenius equation? What does each term mean?

Answer 22

k = Ae^(-Ea/RT)
k - rate constant for equation
A - pre-exponential factor
R - gas constant (8.31)
T - temperature in kelvin
Ea - activation energy for reaction in joules

Question 23

How can you convert the Arrhenius equation into a useful form for plotting a graph?

Answer 23

ln(k) = -Ea/RT + ln(A)

Gradient = -Ea/R
Y intercept is ln(A)