Rates of Reaction (Edexcel GCSE Combined Science: Chemistry): Exam Questions

The rate of a reaction was monitored by recording the volume of gas produced every 5 seconds.

What is the mean rate of reaction in the first 10 seconds of the reaction, in cm³ s^-1?

A student investigated the rate of reaction between dilute hydrochloric acid and marble chips (calcium carbonate).

Calcium chloride, carbon dioxide and water are formed.

Complete and balance the equation for the reaction.

   CaCO₃ + HCl → ....................... + ......................... + ......................

The student investigated the rate by using different sizes of marble chips. In their investigation, the same mass of marble chips was used in each experiment.

The volume of gas given off was measured.

The graph in Figure 8 shows the results.

Figure 8

i) State how the graph shows that line B gives the results for the larger marble chips.

(1)

ii) A tangent has been drawn on line A.

Calculate the rate of reaction at this point.

(2)

rate of reaction =.............................................................cm³ s⁻¹

During any reaction, reactants are used up and the rate of reaction decreases.

Explain, in terms of particles, why the rate of reaction decreases.

The decomposition of hydrogen peroxide is catalysed by adding a small amount of manganese(IV) oxide.

Which of these graphs shows the mass of the catalyst as the reaction takes place?

☐	A
☐	B
☐	C
☐	D

Two gases, X and Y, react to give a gaseous product Z.

The reaction is carried out under two different sets of conditions in experiments 1 and 2 as shown in Figure 9.

Figure 9

Explain why it is not possible to predict what the rate of Experiment 2 will be compared with Experiment 1.

Hydrogen peroxide, H₂O₂, quickly decomposes to produce water and oxygen when a catalyst is added to the solution:

2H₂O₂ (aq) → 2H₂O (l)  + O₂ (g)

The volume of gas produced was measured and is shown in the graph below:

Which statement is not true for this reaction?

Hydrogen peroxide decomposes to form water and oxygen.

The rate of this reaction can be found by measuring the volume of oxygen formed after different time intervals.

Hydrogen peroxide solution is placed in a conical flask. The apparatus is set up as shown in Figure 5.

Figure 5

State the name of the piece of apparatus labelled Z in Figure 5.

At the end of the reaction the bung is removed from the conical flask.
A glowing splint is put into the gas in the flask.

State what you would see.

A solid catalyst can be used for this reaction.

i) The experiment is repeated under identical conditions but with the catalyst added. In the experiment with the catalyst added

(1)

ii) At the end of the experiment with the catalyst added, the mass of the catalyst remaining is found.

The method used to find the mass of the catalyst remaining is

filter the mixture of products and catalyst determine the mass of the filter paper and solid catalyst

subtract the mass of a filter paper from the mass of filter paper and solid catalyst.

This method would not give the accurate mass of catalyst remaining.

Which of the following needs to be done to give a more accurate mass?

(1)

iii) A given mass of catalyst is more effective if it has a large surface area.

State how you could increase the surface area of some lumps of solid catalyst.

(1)

The experiment is repeated three times

once using a more dilute solution of hydrogen peroxide
once using a lower temperature
once using a larger flask

In each case, all other conditions are kept the same.

Circle the word that shows the change in the rate of decomposition in each case.

Complete the balanced equation for the reaction and fill in the two missing state symbols.

.......... H₂O₂ (aq) 2H₂O (..........) + O₂ (..........)

Magnesium metal reacts with an excess of hydrochloric acid solution to form magnesium chloride and hydrogen:

Mg (s) + 2HCl (aq) → MgCl₂ (aq) + H₂ (g)

Which of the following will not increase the rate of this reaction?

The word equation for the reaction between magnesium and dilute hydrochloric acid is

magnesium + hydrochloric acid → magnesium chloride + hydrogen

The reaction was carried out using the apparatus shown in Figure 11.

Figure 11

A strip of magnesium ribbon was placed in the conical flask.

100 cm³ of dilute hydrochloric acid was added to the conical flask.

The mass of the flask and contents was measured at regular intervals.

The loss in mass was calculated.

Figure 12 shows a graph of the results.

Figure 12

Name the apparatus that could be used to measure out 100 cm³ of dilute hydrochloric acid.

Explain why there is a loss in mass of the flask and contents.

The graph shows that the rate of reaction slows as the reaction takes place.

Explain, in terms of particles, why the rate of reaction between magnesium ribbon and dilute hydrochloric acid slows as the reaction takes place.

The experiment was repeated using the acid at a higher temperature.
All other conditions were kept the same.

State the effect of the higher temperature on the mass loss after two minutes.

The original experiment was repeated using the same mass of magnesium powder instead of the magnesium ribbon.

All other conditions were kept the same.

 Sketch, on the graph in Figure 12, the line you would expect for this experiment.

Some reactions are affected by the presence of a catalyst.

i) State the effect of a catalyst on a reaction.

(1)

ii) Devise a simple experiment to find out what happens to the mass of a solid catalyst during a reaction.

(3)

Catalysts are often used in chemical reactions.

Which letter represents two correct features of catalysts?

Calcium carbonate reacts with dilute hydrochloric acid to produce calcium chloride, water and carbon dioxide.

CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂

A student wanted to measure the amount of gas produced in two minutes.

The student suggested that this could be done by counting the number of bubbles formed. However, the bubbles are produced too quickly to count them.

Figure 4 shows a conical flask in which the calcium carbonate and dilute hydrochloric acid are reacting.

Complete Figure 4 to show the apparatus that could be used to measure accurately the volume of gas given off in two minutes.

Figure 4

The reaction between calcium carbonate and dilute hydrochloric acid is exothermic.

Explain, in terms of bond breaking and bond making, why some reactions are exothermic.

An investigation was carried out into the rate of reaction of calcium carbonate with dilute hydrochloric acid.

5.0 g of small lumps of calcium carbonate were reacted with 50 cm³ of 0.50 mol dm^–3 hydrochloric acid. Another 5.0 g of the same sized lumps of calcium carbonate were reacted with 50 cm³ of 1.0 mol dm^–3 hydrochloric acid. The volume of gas collected in two minutes was recorded for each experiment.

The two experiments were then repeated, each using 5.0g of large lumps of calcium carbonate. Figure 5 shows the results.

Figure 5

Explain, in terms of collision of particles, how these results show the effect of the size of the lumps of calcium carbonate and the effect of the concentration of the acid on the rate of this reaction.

Calcium carbonate reacts with hydrochloric acid to produce calcium chloride, water and carbon dioxide:

CaCO₃ (s) + 2HCl (aq) → CaCl₂ (aq) + H₂O (l) + CO₂ (g)

Which statement is not true if the temperature of the reaction decreases?

Calcium carbonate reacts with dilute hydrochloric acid to produce carbon dioxide gas.

The rate of reaction between calcium carbonate and dilute hydrochloric acid at room temperature was investigated.

i) The investigation was carried out with different sized calcium carbonate pieces.

The mass of calcium carbonate and all other conditions were kept the same.

The results are shown in Figure 15.

Figure 15

State, using the information in Figure 15, the effect of the surface area of the calcium carbonate on the rate of this reaction.

(1)

ii) The calcium carbonate powder produced 90 cm³ of carbon dioxide in five minutes. Calculate the average rate of reaction in cm³ s^-1. (3)

average rate of reaction = ......................................... cm³ s^-1

iii) The experiments were repeated at a higher temperature. The rate of reaction for each experiment increased.

Explain, in terms of particles, why the rate of reaction increased when the temperature was increased.

(3)

Zinc metal reacts with dilute hydrochloric acid to produce hydrogen gas.

zinc + hydrochloric acid → zinc chloride + hydrogen

A student investigated the effect of doubling the concentration of the hydrochloric acid on this reaction. The student made the following prediction.

When the concentration of the hydrochloric acid is doubled the rate of reaction will double and the reaction will be more exothermic.

Devise a plan, including the apparatus you would use, to test the student’s prediction.

You are provided with pieces of zinc and two bottles of dilute hydrochloric acid.

One bottle of hydrochloric acid is double the concentration of the other.

Magnesium reacts with hydrochloric acid to produce magnesium chloride and hydrogen gas:

Mg (s) + 2HCl (aq) MgCl₂ (aq) + H₂ (g)

During the first 10 s of the reaction, 1.2 g of magnesium was used up.

Calculate the mean rate of reaction, in mol s^-1, for this part of the reaction.

Relative atomic masses (A_r): H = 1, Mg = 24 and Cl = 35.5.

Magnesium reacts with dilute sulfuric acid to form magnesium sulfate and hydrogen gas.

A student wants to find out the effect of temperature on the rate of this reaction.

The student used the following method.

The student kept the volume of sulfuric acid the same when they repeated the method at 50 °C.

State two other variables that should be kept the same.

Which piece of equipment that can be used to find the volume of 25 cm³ of sulfuric acid?

State how the student will know that the reaction has finished.

The reaction at 50 °C was faster than the reaction at 30 °C.

Give one reason, in terms of particles, why the reaction at 50 °C was faster than the reaction at 30 °C.

At 50 °C, 15.0 cm³ of gas was produced during the first 60 seconds of the reaction.

Calculate the average rate of reaction, in cm³ s^–1, for the first 60 seconds of the reaction.

A student wants to investigate the effect of surface area on the rate of reaction between marble chips and dilute acid.

What pieces of apparatus could be used for this investigation?

Figure 9 shows a sample of hydrogen peroxide solution decomposing to form water and oxygen gas.

Figure 9

i) Write the word equation for hydrogen peroxide solution decomposing.

(1)

...............................    →    ...............................

ii) In this reaction hydrogen peroxide is a solution, water is a liquid and oxygen is a gas.

Draw one straight line from each substance to its correct state symbol.

(2)

Describe the test to show the gas produced is oxygen.

Figure 10 shows the electron arrangement for an atom of hydrogen and an atom of oxygen.

Figure 10

Complete the dot and cross diagram in Figure 11 for a molecule of water, H₂O.

Draw outer shell electrons only.

Figure 11

Liver contains the enzyme catalase.

A piece of liver was added to another sample of hydrogen peroxide solution.

Figure 12 shows the results.

Figure 12

Figure 13 shows a graph of the volume of oxygen produced from the hydrogen peroxide with and without liver.

Figure 13

i) Complete the missing label on the axis of the graph.

(1)

ii) Describe what the graph shows about the difference in decomposition of hydrogen peroxide with and without liver.

(2)

iii) Describe how the apparatus in Figure 12 could be modified to find the volume of gas produced when the liver is added to the hydrogen peroxide.

(2)

This question is about the rate of reaction between calcium carbonate and dilute hydrochloric acid.

The word equation for this reaction is         calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide

Which of the following is the formula for calcium carbonate?

Some pieces of calcium carbonate were added to dilute hydrochloric acid in a conical flask and the volume of carbon dioxide produced was measured.

Complete the diagram in Figure 7 to show the apparatus to collect the gas produced and measure its volume.

Figure 7

The reaction between calcium carbonate and dilute hydrochloric acid was investigated at different temperatures.

i) State what could be used to keep the temperature of the conical flask and its contents at a temperature of 45 °C throughout the reaction. (1)

ii) Figure 8 shows a graph of volume of gas collected in this investigation.

Figure 8

Draw a tangent at 100 seconds on Figure 8. Use this tangent to calculate the rate of reaction at this time.

(2)

rate of reaction = ................................ cm³ s^-1

iii) The temperature of the acid was kept at 45 °C. State one other variable that needs to be controlled during this investigation.

(1)

iv) Explain, in terms of particles, how decreasing the temperature affects the rate of this reaction.

(3)