Syllabus Edition

First teaching 2023

First exams 2025

|

How Fast? The Rate of Chemical Change (SL IB Chemistry)

Exam Questions

4 hours57 questions
1a2 marks

Describe kinetic theory in relation to energy and temperature.

1b2 marks

State what is required for a collision to result in a reaction.

1c2 marks

State the meaning of activation energy (Ea).

1d1 mark

Label the activation energy on the energy profile diagram below.

6-1-ib-sl-sq-easy-q1d-energy-profile-diagram

Did this page help you?

2a3 marks
State three ways of monitoring concentration changes in a reaction.
2b1 mark
A reaction is monitored by measuring the volume of a gas produced every 10 seconds. State an appropriate unit to use.
2c4 marks
Sketch a graph to show the volume of gas produced during the course of an experiment against the time taken.
2d1 mark
State the effect that increasing concentration has on the rate of a reaction.

Did this page help you?

3a1 mark

State the effect that increasing temperature has on the rate of a reaction.

3b3 marks

Sketch a line on the graph to show the same reaction occurring at a higher temperature.

6-1-ib-sl-sq-easy-q4d-rate-of-reaction-graph-sketch
3c2 marks

State two variables that need to be controlled when investigating the effect of temperature on rate in the following reaction:

2HCl (aq) + Mg (s) rightwards arrowMgCl2 (aq) + H2 (g)
3d1 mark

Suggest an appropriate piece of equipment to use to measure the volume of H2 gas produced in the reaction between HCl and Mg.

Did this page help you?

4a2 marks

Sketch a line on the potential energy profile diagram to show the pathway for the same reaction, but with a catalyst.


6-1-ib-sl-sq-easy-q1d-energy-profile-diagram
4b3 marks

Explain how catalysts work.

4c2 marks

 Maxwell-Boltzmann distribution is shown below:

6-1-ib-sl-sq-easy-q4c-maxwell-boltzmann-curve
i)
Draw a line on the Maxwell-Boltzmann curve below to show the effect of adding a catalyst.
[1]
ii)
Shade in the area representing the number of particles that can react with the catalyst present.
[1]
4d3 marks

Sketch a line on the graph to show the same reaction occurring with a catalyst.


6-1-ib-sl-sq-easy-q4d-rate-of-reaction-graph-sketch

Did this page help you?

52 marks

Outline two ways a rate of a reaction can be expressed and state the units for rate of reaction.

Did this page help you?

6a3 marks

The Arrhenius equation can also be written in natural logarithmic forms.

ln k = ln A - fraction numerator E subscript a over denominator R T end fraction

A plot of ln k against 1 over T gives a straight-line graph of the type y = mx + c.

Complete the table below which relates the terms from the natural logarithmic Arrhenius equation to the equation of a straight line.

Straight-line term

Arrhenius term

y

ln k 

m

 

x

 

c

 

6b
Sme Calculator
2 marks

A graph of ln k against 1 over T is shown below.

arrhenius-graph

 Calculate the gradient of the straight line.

6c
Sme Calculator
1 mark

Using section 2 of the data booklet, calculate the activation energy, Ea for the graph in part b).

6d
Sme Calculator
2 marks

Calculate the frequency factor, A, for the graph in part b) to 2 decimal places.

Did this page help you?

7a1 mark

Arrhenius plots for two reactions with different activation energies are shown below.

arrhenius-graph-question-

State which plot shows the reaction with the greatest activation energy.

7b1 mark

The temperature of both reactions from part a) is increased from 20° to 45°.

Using section 1 of the data booklet, determine which of the reactions will experience the largest change in the rate of reaction.

7c
Sme Calculator
2 marks

The decomposition of hydrogen peroxide into water and oxygen occurs at a slow rate with a rate constant of k = 6.42 x 10-4 mol dm-3 s-1 and at a temperature of 290 K.

When the temperature is increased to 340 K the rate constant k = 6.47 x 10-2 mol dm-3 s-1.

Using sections 1 and 2 of the data booklet, calculate the activation energy for this reaction.

Did this page help you?

1a4 marks

In any chemical reaction, the particles will all be moving around in different directions, at different speeds, with different amounts of energy.

A Maxwell-Boltzmann distribution is a graph which shows the distribution of energy amongst particles within a chemical reaction. 

Figure 1 below shows the Maxwell-Boltzmann distribution in a sample of a gas at a fixed temperature, T1

Figure 1RTYjz6v0_1

i)
Label the x and y axes of the graph.
[2]
ii)
Sketch a distribution for this same sample of gas, at a higher temperature, and label it as T2.
[2]
1b2 marks

State why a Maxwell-Boltzmann distribution curve always starts at the origin and what the area under the curve represents.

1c3 marks

Chemical reactions take place at different speeds. For a chemical reaction to take place, particles must collide with each other in the correct orientation and with sufficient energy. 

i)
Explain why most collisions between particles in the gas phase do not result in a reaction taking place.
[1]
ii)

State and explain one way that the rate of reaction could be increased, other than by increasing the temperature.

[2]

1d1 mark

Give one reason why a reaction may be slow at room temperature.

Did this page help you?

2a1 mark

State the meaning of the term rate of reaction.

2b3 marks

A group of students were completing a practical, investigating the factors which affect the rate of the chemical reaction shown below. 

A (s) + B (aq) → C (g)

The students collected the gas produced and plotted the graph shown in Figure 1

Figure 1

rUppbj5Q_2

i)
State and explain what the letter R represents on the students graph in Figure 1.
[1]
ii)

In the original reaction above, the students used 0.5 g of A and 50 cm3 of 1.0 mol dm-3 B.         

Sketch a curve on the graph to show how the total volume of gas collected would change if the students still used 0.5 g of A, but used 50 cm3 of 2.0 mol dm-3 of B.

[2]

2c2 marks

Explain why the gradient of the curve in part (b) decreases as the time of the reaction progresses.

2d2 marks

Another way to increase the rate of reaction is to increase the temperature. 

Explain why a small increase in temperature has a large effect on the initial rate of a chemical reaction.  

Did this page help you?

3a1 mark

The decomposition of hydrogen peroxide into water and oxygen is a very slow chemical reaction. 

Write the equation for the decomposition of hydrogen peroxide.

3b5 marks

The rate of decomposition of hydrogen peroxide can be found by collecting and measuring the volume of gas formed at specific time intervals.

i)
Draw a labelled diagram to show the apparatus that you would use to collect and measure the volume of gas formed during this reaction. 
[2]
ii)
Explain how you would use the results to determine the initial rate of the reaction.
[3]
3c1 mark

The decomposition of hydrogen peroxide is a slow reaction, so a catalyst is often added to speed up the rate of the reaction. Catalysts are used in many chemical reactions to increase the rate.

The following shows a two-step reaction mechanism of a chemical reaction, where a catalyst, X is used. 

STEP 1:                                  W + X  →  Y + Z

STEP 2:                                  Y + W → Z + A + X

OVERALL REACTION:         2W → 2Z + A

Give a reason, other than the rate of reaction increasing, why it can be deduced from the three equations above that X is a catalyst.

3d1 mark

The graph shown below represents the decomposition of hydrogen peroxide.

Figure 1

question-3d-figure-1

The graph starts to level out as the reaction slows down.

State why the rate of the reaction slows down over time.  

Did this page help you?

4a2 marks

During the following reaction, A and B react together to produce C

A  +  2B    C

Figure 1 shows the production of C over time.   

Figure 1

lJm_oKlA_3

i)
Sketch a graph to show what happens to A and B during the progress of the reaction. 
[1]
ii)
On your graph, write the letter E at the point at which an equilibrium is first established. 
[1]
4b3 marks

In the reaction in part (a), large pieces of A were used.

Use collision theory to explain what would happen to the rate of the reaction if powdered A was used instead of large pieces.

4c6 marks

In a different reaction, gaseous W and X were added together to produce Y and Z as shown in the equation below:

2W (g)  +  X (g)  →  Y (g)  + 2Z (g)

A catalyst was added to speed up the rate of reaction. 

i)
Sketch a Maxwell-Boltzmann distribution on the axes below in Figure 2 to show the distribution of molecular energies at a constant temperature with and without a catalyst.
Use Ea to label the activation energy without a catalyst and Ec to label the activation energy with a catalyst.
[3]
ii)

Explain what your distribution shows. 

[3]

Figure 2

P5iChsAC_7

4d6 marks

Some changes were made individually to the experiment completed in part (c). 

Consider your Maxwell-Boltzmann distribution curve from part (c). For each of the changes in parts (i), (ii) and (iii) below, state and explain the effect that the change would have on:

  • The area under the curve 
  • The value of the most probable energy of the molecules (Emp
  • The proportion of molecules with energy greater than or equal to Ea
i)

The temperature of the original reaction is increased, but no other changes are made.

[2] 

ii)

The number of molecules in the original reaction mixture is increased, but no other changes are made.

[2] 

iii)

A catalyst is added to the original reaction mixture, but no other changes are made.

[2]

Did this page help you?

5a1 mark

Iodine reacts with propanone in an acid catalyzed reaction, according to reaction equation below.  

CH3COCH3 (aq) + I2 (aq) → CH3COCH2I (aq) + H+ (aq) + I- (aq)

Suggest how the change in concentration of iodine could be used to determine the rate of the above reaction.  

5b2 marks

A group of students completed the iodination of propanone reaction using the same acid catalyst, but with different concentrations. The results achieved are shown in the table below:

Table 1

Concentration of acid, [H+/ moldm-3

Relative Rate of Iodination Reaction

0.100

0.0046

0.200

0.0092

0.300

0.0138


Use the table to state and explain the relationship between the concentration of acid used in the reaction and the rate.

5c1 mark

Sodium thiosulfate and hydrochloric acid will react together readily, as shown by the equation below:

Na2S2O3  +  2HCl  →  2NaCl  +  S  +  SO2  +  H2O

This reaction is often referred to as the ‘disappearing cross’ experiment. The cross disappears when viewed from above because the solution turns cloudy as a sulfur precipitate is formed, covering the cross.  

Figure 1

question-5c-figure-1

The speed of the reaction can be increased, by raising the temperature of the sodium thiosulfate solution in the reaction. The thiosulfate solution is heated to different temperatures before the acid is added, and the time it takes for the cross to disappear is recorded. The times can then be compared.

Suggest one reason why the value for the rate of reaction when a higher temperature was used may be less accurate than at a lower temperature.

5d3 marks

Collision theory can be used to explain why different factors affect the rate of a chemical reaction.

Describe collision theory.

Did this page help you?

6a3 marks

A student carried out a metal displacement reaction between zinc powder and copper(II) sulfate solution. The equation for the reaction is

Zn (s) + CuSO4 (aq) → ZnSO4 (aq) + Cu (s)

3.78 g of zinc powder was added to 50.0 cm3 of 0.250 moldm-3 copper(II) sulfate solution.

Determine the limiting reagent showing your working.

6b2 marks

The reaction between the zinc and copper sulfate was carried out in a polystyrene cup and the temperature change was measured using a temperature probe. The maximum temperature rise the student recorded was 8.5 oC. 

Using sections 1 and 2 of the data booklet, calculate the enthalpy change, H, for the reaction, in kJ.

Assume that all the heat evolved was absorbed by the solution, and that the density and specific heat capacity of the copper(II) sulfate solution are the same as pure water.

6c2 marks

State two further assumptions made in the calculation of H.

6d4 marks

Using Figure 1, sketch a graph of the concentration of zinc sulfate, ZnSO4 (aq), versus time and show how the graph may be used to find the initial rate of reaction.

                                                                  Figure 111-2-ib-chemistry-sq-q2d-medium

Did this page help you?

7a4 marks

A student investigated the rate of decomposition of hydrogen peroxide, H2O2, at a temperature of 45 o The decomposition reaction occurs in the presence of a catalyst, MnO2.

 2 straight H subscript 2 straight O subscript 2 space left parenthesis aq right parenthesis space space rightwards arrow with space MnO subscript 2 on top space space space straight O subscript 2 space left parenthesis straight g right parenthesis space plus space 2 straight H subscript 2 straight O space left parenthesis straight l right parenthesis           

The results she obtained are shown in Table 1 below.

Table 1

Time / s

Concentration of H2O2 / moldm-3

Time / s

Concentration of H2O2 / moldm-3

0

0.200

120

0.068

20

0.155

140

0.063

40

0.124

160

0.058

60

0.102

180

0.055

80

0.085

200

0.052

100

0.075

 

 

 

Plot a graph on the axes below in Figure 1 and from it determine the rate of reaction after 60 s.

Figure 1

11-2-ib-chemistry-sq-q5a-medium

7b3 marks

On the same graph sketch the shape obtained if the student had carried out the same reaction at 60 oC. Explain the shape of the graph at 60 oC.

7c3 marks

The decomposition of hydrogen peroxide can be investigated by measuring the volume of oxygen given off using the apparatus shown in Figure 2.

Figure 2

11-2-ib-chemistry-sq-q5c-medium

i)
Explain why the volume of oxygen given off can be used as a measure of the concentration of hydrogen peroxide. 
[1]
ii)
Suggest one limitation of using the apparatus used in Figure 2.
[1]
iii)
Suggest an alternative method of measuring the rate of reaction.
[1]
7d2 marks

Two students decide to measure the rate of decomposition for H2O2 using the change in mass as oxygen escapes from the reaction container.

One student says that they should use a three decimal place rather than two decimal place balance because it will make their results more accurate. The second student disagrees and says it will make their results more precise, but not more accurate.

Which student is correct?

Did this page help you?

82 marks

Explain why the reaction represented below is a redox reaction. 

2ClO2 (aq) + 2NaOH (aq) → NaClO3 (aq) + NaClO2 (aq) + H2O (l) 

Did this page help you?

9a3 marks

The decomposition of hydrogen peroxide into water and oxygen occurs at a slow rate with a rate constant of k = 6.62 x 10-3 mol dm-3 s-1 and at a temperature of 290 K. 

Using Sections 1 and 2 of the Data Booklet, calculate the activation energy, Ea, correct to three significant figures and state its units.

The constant, A = 3.18 × 1011 mol−1 dm3.

9b2 marks

Hydrogen peroxide decomposes to form water and oxygen as shown in the equation below.

2H2O2 (aq) → 2H2O (l) + O2 (g) 

The table below shows the value of the rate constant at different temperatures for a reaction.

Rate constant k / s-1

ln k

Temperature / K

 italic 1 over italic T

0.000493

 

295

 

0.000656

 

298

 

0.001400

 

305

 

0.002360

 

310

 

0.006120

 

320

 

Complete the table by calculating the values of ln k and begin mathsize 14px style italic 1 over italic T end style at each temperature.

9c4 marks

The results of the experiment can be used to calculate the activation energy, Ea. Use the results table to plot a graph of ln k against begin mathsize 14px style italic 1 over italic T end style.

q1c_16-2_ib_hl_medium_sq

9d4 marks

Using Sections 1 and 2 of the Data Booklet and your graph, calculate a value for the activation energy, Ea, for this reaction. To gain full marks you must show all of your working.

Did this page help you?

10a3 marks

The Arrhenius equation can be represented as k = Ae to the power of negative E a divided by R T end exponent in its exponential form.

 State the effect on k of an increase in; 

i)     The constant, A, (frequency factor) 

[1]

ii)     Activation energy, Ea 

[1]

iii)    Temperature, T

[1]

10b2 marks

Using Sections 1 and 2 of the Data Booklet, calculate the activation energy, Ea, of a reaction at 57 oC and a rate constant of 1.30 x 10-4  mol dm-3 s-1.

The constant A = 4.55 × 1013.

10c3 marks

The table below shows how temperature affects the rate of reaction.

Rate constant k/s-1

ln k

Temperature / K

 italic 1 over T

2.0 x 10-5

-10.8

278

0.00360

4.7 x 10-4

-7.7

298

0.00336

1.7 x 10-3

-6.4

308

0.00325

5.2 x 10-3

-5.3

318

0.00314

 

Use the results to plot a labelled graph of ln k against begin mathsize 14px style italic 1 over italic T end style.q2c_16-2_ib_hl_medium_sq

10d4 marks

Using Sections 1 and 2 of the Data Booklet and your graph, calculate a value for the activation energy, Ea, for this reaction.

Did this page help you?

11a2 marks

An Arrhenius plot of ln k against italic 1 over T for the reaction between A (g) and B (g) at different temperatures is shown in Figure 1 below.

q4b_16-2_ib_hl_medium_sq

The equation of the line of best fit was found to be: 

            ln k = -6154begin mathsize 14px style begin italic style stretchy left parenthesis 1 over italic T stretchy right parenthesis end style end style - 8.2 

Calculate the activation energy, Ea, for the reaction between A (g) and B (g).

11b2 marks

Define the Arrhenius constant, A.

11c2 marks

Using the Arrhenius plot, calculate an approximate value for the constant, A.

Did this page help you?

12a1 mark

The graph of ln k against begin mathsize 14px style italic 1 over italic T end style for a general reaction is shown.q5a_16-2_ib_hl_medium_sq



Sketch the expected line for a different reaction with a higher activation energy.

12b2 marks

A graph of ln k against begin mathsize 14px style italic 1 over italic T end style for another general reaction is shown.q5b_16-2_ib_hl_medium_sq

 

Sketch the expected line for the same reaction with an added catalyst.

12c3 marks

Rate constant data for the reaction of hydrogen and iodine at two different temperatures is shown in the table below. 

H2 (g) + I2 (g) → 2HI (g) 

Table 1

Experiment

Temperature / K

Rate constant, k / mol dm-3 s-1

1

599

5.40 x 10-4

2

683

2.80 x 10-2

            

Using Sections 1 and 2 of the Data Booklet, calculate the activation energy, in kJ mol-1, for the reaction.

12d2 marks

Using the data from experiment 1 and Sections 1 and 2 in the Data Booklet, calculate a value for the constant, A.

Table 2

Experiment

Temperature / K

Rate constant, k / mol dm-3 s-1

1

599

5.40 x 10-4

2

683

2.80 x 10-2

Did this page help you?

1a2 marks

A group of students planned how to investigate the effect of changing the concentration of H2SO4 on the initial rate of reaction with magnesium: 

Mg (s) + H2SO(aq) rightwards arrowMgSO4 (aq) + H2 (g) 

They decided to measure how long the reaction took to complete when similar masses of magnesium were added to acid. 

Two methods were suggested:

Method 1 - Use small pieces of magnesium ribbon, an excess of acid and record the time taken for the magnesium ribbon to disappear

Method 2 - Use large strips of magnesium ribbon, an excess of magnesium and record the time taken for bubbles to stop forming 

Deduce, giving a reason, which of method 1 and method 2 would be the least affected if the masses of magnesium ribbon used varied slightly between each experiment.

1b2 marks

Neither method in part a) actually allows the initial rate to be calculated. Outline a method that would allow the calculation of initial rate.

1c1 mark

The reaction is to be conducted across a few weeks.

State a factor that has a significant effect on reaction rate, which could vary between experiments across the weeks and therefore needs to be controlled.

1d
Sme Calculator
4 marks

One group collected the following data using 1.50 mol dm-3 acid:

 
 
Trial Time/ s (plus-or-minus 0.01 s)
1 91.56
2 98.33
3 72.08
4 89.41

i)
Comment on the use of uncertainty when calculating the mean.
[2]
ii)
Calculate the mean time for the set of results.
[2]

Did this page help you?

2a5 marks

When investigating the reaction between sulfuric acid and calcium carbonate, it was observed that a small increase of temperature of around 10 oC caused a doubling in the rate of the reaction.

Sketch and label Maxwell-Boltzmann curve for the two temperatures T and T+10, and use this diagram to help to explain this effect of temperature on rate.

2b2 marks
Why do some collisions at high temperatures still not result in the formation of the product?
2c3 marks

Identify and explain another factor that affects the number of particles present in a solution with sufficient energy to react.

2d2 marks

Some groups investigating the effect of temperature on rate stirred their reactions, some did not.

Explain the effect of stirring upon the rate of the reaction.

Did this page help you?

3a5 marks

0.5 g of magnesium reacts with 50 cm3 of 0.01 moldm-3 nitric acid. Magnesium is in excess.

A graph monitoring the volume of hydrogen gas produced is shown below:

6-1-ib-sl-sq-hard-q3a-rate-of-reaction-graph
i)
Calculate the mean rate of reaction over the first 15 seconds of the reaction
[1]
ii)
Calculate the actual rate of reaction at 15 seconds
[3]
iii)
Explain the difference in values for rate
[1]
3b3 marks

Compare the expected rate and progress of the reaction if 25 cm3 of 0.2 mol dm-3 nitric acid was used instead of 50 cm3 of 0.1 mol dm-3 nitric acid.

3c2 marks

Suggest one change to the reaction that could be made to produce more hydrogen gas in total and explain your choice.

3d2 marks

Suggest why it is often better to study a slower reaction instead of a faster one.

Did this page help you?

4a1 mark

The following energy profile diagram shows the pathways for both a catalysed and uncatalysed reversible reaction:

6-1-ib-sl-sq-hard-q4a-energy-profile-diagram

Identify the letter(s) representing the activation energy for the catalysed reverse reaction.

4b2 marks

State and explain the effect that this catalyst will have on the equilibrium yield.

4c2 marks

Vehicles with combustion engines usually have catalytic convertors added to catalyse the oxidation of carbon monoxide into carbon dioxide and to catalyse the reduction of nitrogen oxides to nitrogen. These catalysts are usually rhodium or platinum.

Leaded fuels were phased out as they were found to poison these catalysts, binding irreversibly to the metal surface.

Explain the problems for drivers of the catalysts being poisoned.

4d1 mark

Suggest a situation in which using a catalyst would not be appropriate.

Did this page help you?

5
Sme Calculator
2 marks

The reaction between iodide ions and persulfate ions is a 'clock' reaction and often used to study reaction kinetics.

2I- (aq) + S2O82- (aq) → I2 (aq) + 2SO42- (aq)

Deduce the redox changes taking place in the reaction.

Did this page help you?

6a
Sme Calculator
3 marks

A series of experiments were carried out to investigate how the rate of the reaction of bromate and bromide in acidic conditions varies with temperature.

The time taken, t, was measured for a fixed amount of bromine to form at different temperatures. The results are shown below. 

Temperature (T) / K

1 over Tx 10-3 / K-1

Time (t) / s

1 over t/ s-1

ln1 over t

408

2.451

21.14

0.0473

-3.051

428

2.336

10.57

   

448

 

5.54

0.1805

-1.712

468

2.137

3.02

0.3311

-1.106

488

2.049

   

-0.536

 

Complete the table above.

6b
Sme Calculator
4 marks

The Arrhenius equation relates the rate constant, k, to the activation energy, Ea, and
temperature, T.

ln k = ln A + fraction numerator negative E subscript a over denominator R T end fraction

In this experiment, the rate constant, k, is directly proportional to 1 over t. Therefore, 

ln 1 over t= ln A + fraction numerator negative E subscript a over denominator R T end fraction

Use your answers from part (a) to plot a graph of ln 1 over t against 1 over Tx 10-3 on the graph below.

graph

6c
Sme Calculator
4 marks

Use section 2 of the data booklet along with your graph and information from part (b) to calculate a value for the activation energy, in kJ mol–1, for this reaction.

To gain full marks you must show all of your working.

Did this page help you?

7a
Sme Calculator
2 marks

The rate constant for a reaction doubles when the temperature is increased from 25.0 °C to 35 °C.

Calculate the activation energy, Ea, in kJ mol−1 for the reaction using section 1 and 2 of the data booklet.

7b2 marks

A different reaction route is used which reduces the activation energy of the reaction. 

Explain how the rate constant calculated in part(b) would differ.

Did this page help you?