Rate of Reaction Practice Questions

Question 1

4 marks

Hydrogen peroxide solution slowly decomposes to form water and oxygen.

$2\mathrm{H_2O_2(aq)} \rightarrow 2\mathrm{H_2O(l)} + \mathrm{O_2(g)}$

A student wants to follow the rate of this reaction in the laboratory.

(a)

Give two factors, other than adding a catalyst, that can change the rate of a chemical reaction.

/ 2

(b)

Describe how the student could follow the rate of this reaction by measuring the oxygen produced.

/ 2

Question 2

4 marks

A student added an excess of small calcium carbonate chips to $50\ \mathrm{cm^3}$ of dilute hydrochloric acid in a conical flask.

The flask was plugged with cotton wool and placed on a balance.

Mass of flask and contents at the start $= 152.40\ \mathrm{g}$
Mass of flask and contents after $250\ \mathrm{s}$ (reaction complete) $= 150.15\ \mathrm{g}$

(a)

Explain why the mass of the flask and contents decreases during the reaction.

/ 1

(b)

Calculate the mean rate of this reaction over the $250$ seconds.

Give your answer in $\mathrm{g/s}$ .

/ 2

(c)

Give one reason why cotton wool is used to plug the flask instead of a rubber bung.

/ 1

Question 3

3 marks

Sodium thiosulfate solution reacts with dilute hydrochloric acid.

A student put a conical flask containing the two solutions on top of a paper cross and timed how long it took for the cross to be no longer visible when viewed from above.

The student repeated the experiment using different concentrations of sodium thiosulfate solution.

Table 1

Concentration of sodium thiosulfate in $\mathrm{mol/dm^3}$	Time for the cross to disappear in s
0.020	196
0.030	131
0.040	98
0.050	79
0.060	66

(a)

Explain why the cross can no longer be seen.

/ 1

(b)

Describe the relationship between the concentration of sodium thiosulfate solution and the time for the cross to disappear, shown in Table 1.

/ 1

(c)

Give one variable the student must control to make this a fair test.

/ 1

Question 4

4 marks

A student reacted $0.05\ \mathrm{g}$ of magnesium ribbon with an excess of dilute hydrochloric acid and measured the volume of hydrogen produced.

The experiment was carried out twice, once at $20\ ^\circ\mathrm{C}$ and once at $40\ ^\circ\mathrm{C}$ .

Figure 1 shows the results.

(a)

Use Figure 1 to give the total volume of hydrogen produced at $40\ ^\circ\mathrm{C}$ .

/ 1

(b)

Use Figure 1 to give the time at which the reaction at $20\ ^\circ\mathrm{C}$ finished.

/ 1

(c)

Give one way Figure 1 shows that the reaction at $40\ ^\circ\mathrm{C}$ is faster.

/ 1

(d)

Both reactions produce the same total volume of hydrogen. Suggest why.

/ 1

Question 0

4 marks

A student placed a $3\ \mathrm{cm}$ strip of magnesium ribbon into $25\ \mathrm{cm^3}$ of hydrochloric acid and timed how long it took for the magnesium to disappear.

The experiment was repeated at $25\ ^\circ\mathrm{C}$ with different concentrations of acid.

Table 2

Concentration of hydrochloric acid in $\mathrm{mol/dm^3}$	Time for the magnesium to disappear in s
0.5	240
1.0	120
2.0	60

(a)

The student repeated the experiment using hydrochloric acid of concentration $4.0\ \mathrm{mol/dm^3}$ .

Predict the time for the magnesium to disappear.

/ 1

(b)

Explain, in terms of collision theory, why the time for the magnesium to disappear halves each time the concentration of the acid is doubled.

/ 3

Question 0

5 marks

A student investigated the effect of temperature on the rate of the reaction between marble chips and dilute hydrochloric acid.

The student measured the time taken to collect $40\ \mathrm{cm^3}$ of carbon dioxide in a gas syringe.

Table 3

Temperature in $^\circ\mathrm{C}$	Time to collect $40\ \mathrm{cm^3}$ of carbon dioxide in s
20	90
30	62
40	44
50	31

(a)

Calculate the mean rate of reaction at $30\ ^\circ\mathrm{C}$ .

Give your answer in $\mathrm{cm^3/s}$ to 2 significant figures.

/ 2

(b)

Explain, in terms of collision theory, why increasing the temperature increases the rate of this reaction.

/ 3

Question 0

5 marks

A cube of marble (calcium carbonate) of side $3.0\ \mathrm{cm}$ is added to an excess of dilute hydrochloric acid.

The experiment is then repeated using an identical cube that has been cut into $27$ smaller cubes, each of side $1.0\ \mathrm{cm}$ .

(a)

Show that the surface area to volume ratio of the $3.0\ \mathrm{cm}$ cube is $2:1$ .

/ 2

(b)

Calculate the total surface area of the $27$ small cubes.

/ 1

(c)

Explain why the $27$ small cubes react more quickly with the acid than the single large cube.

/ 2

Question 0

4 marks

A student added manganese(IV) oxide to $50\ \mathrm{cm^3}$ of hydrogen peroxide solution and measured the volume of oxygen collected in a gas syringe every $10$ seconds.

Table 4

Time in s	Volume of oxygen in $\mathrm{cm^3}$
0	0
10	26
20	44
30	56
40	73
50	67
60	68
70	68
80	68

Figure 2

(a)

Complete Figure 2.

You should:

plot the data from Table 4
draw a curve of best fit, ignoring any anomalous result.

/ 3

(b)

Identify the anomalous result and give a reason for your choice.

/ 1

Question 0

5 marks

A student investigated the decomposition of hydrogen peroxide solution.

The student added $1.00\ \mathrm{g}$ of a different solid to $50\ \mathrm{cm^3}$ of hydrogen peroxide solution each time and measured the time taken to collect $50\ \mathrm{cm^3}$ of oxygen.

At the end of each experiment the solid was filtered off, dried and weighed.

Table 5

Solid added	Time to collect $50\ \mathrm{cm^3}$ of oxygen in s	Mass of solid at the end in g
none	420	–
copper(II) oxide	385	1.00
manganese(IV) oxide	25	1.00
zinc oxide	415	1.00

(a)

Identify the solid that is the best catalyst for this reaction.

Give a reason for your answer, using Table 5.

/ 2

(b)

Give the evidence from Table 5 that shows the catalyst is not used up in the reaction.

/ 1

(c)

Explain how a catalyst increases the rate of a reaction.

/ 2

Question 0

5 marks

A student carried out an investigation into how the concentration of hydrochloric acid affects the rate of its reaction with magnesium ribbon.

This is the method used.

Measure $50\ \mathrm{cm^3}$ of hydrochloric acid of concentration $0.5\ \mathrm{mol/dm^3}$ into a conical flask.
Add a $4\ \mathrm{cm}$ piece of magnesium ribbon and immediately fit a bung with a delivery tube leading to a gas syringe.
Record the volume of hydrogen in the gas syringe every $15$ seconds for $3$ minutes.
Repeat steps 1 to 3 with acid of concentration $1.0$ , $1.5$ and $2.0\ \mathrm{mol/dm^3}$ .

(a)

Name the independent variable and the dependent variable in this investigation.

/ 2

(b)

Other than temperature, give one variable the student must keep the same.

/ 1

(c)

In one experiment the student was slow to fit the bung after adding the magnesium.

Explain the effect this would have on the results.

/ 2

Question 0

7 marks

Higher tier

A student added an excess of dilute hydrochloric acid to $0.50\ \mathrm{g}$ of calcium carbonate powder and recorded the volume of carbon dioxide produced.

The student plotted a graph of the volume of carbon dioxide against time and drew a tangent to the curve at $40$ seconds.

The tangent passes through the points $(10\ \mathrm{s},\ 12\ \mathrm{cm^3})$ and $(70\ \mathrm{s},\ 81\ \mathrm{cm^3})$ .

(a)

Explain why the student drew a tangent to the curve instead of calculating a mean rate over the whole reaction.

/ 1

(b)

Calculate the rate of reaction at $40$ seconds, in $\mathrm{cm^3/s}$ .

Give your answer to 2 significant figures.

/ 2

(c)

Calculate the rate of reaction at $40$ seconds in $\mathrm{mol/s}$ .

The volume of one mole of any gas at room temperature and pressure is $24\ \mathrm{dm^3}$ .

/ 2

(d)

The rate of reaction at $100$ seconds is lower than the rate at $40$ seconds.

Explain why.

/ 2

Question 0

6 marks

Figure 3 shows the reaction profile for a reaction carried out with and without a catalyst.

(a)

Use Figure 3 to determine the activation energy of the catalysed reaction.

Give the unit.

/ 1

(b)

Explain, using Figure 3, why the catalysed reaction has a greater rate than the uncatalysed reaction.

/ 3

(c)

A student suggested that the catalyst works by giving the reacting particles more energy.

Explain why the student is wrong.

/ 2

Question 0

7 marks

A student reacted $0.20\ \mathrm{g}$ of magnesium powder with $50\ \mathrm{cm^3}$ of hydrochloric acid and measured the volume of hydrogen produced.

The experiment was repeated using $50\ \mathrm{cm^3}$ of a more concentrated acid. The acid was in excess in both experiments.

Table 6

Time in s	Volume of hydrogen with $1.0\ \mathrm{mol/dm^3}$ acid in $\mathrm{cm^3}$	Volume of hydrogen with $2.0\ \mathrm{mol/dm^3}$ acid in $\mathrm{cm^3}$
0	0	0
20	58	110
40	100	166
60	130	190
80	152	198
100	170	200
120	184	200
140	196	200
160	200	200

(a)

Calculate the mean rate of reaction during the first $20$ seconds for the $2.0\ \mathrm{mol/dm^3}$ acid.

Give the unit.

/ 2

(b)

Both experiments produced a total of $200\ \mathrm{cm^3}$ of hydrogen.

Explain why.

/ 2

(c)

The mean rate of reaction in the first $20$ seconds with $2.0\ \mathrm{mol/dm^3}$ acid is approximately double the mean rate with $1.0\ \mathrm{mol/dm^3}$ acid.

Explain this result using collision theory.

/ 3

Atomic Structure & the Periodic Table

Bonds, Structure & Properties of Matter

Quantitative Chemistry

Chemical Changes

Energy Changes

Chemical Change: Rate & Extent

Organic Chemistry

Chemical Analysis

Chemistry of the Atmosphere

Using Resources

Question 1

Question 2

Question 3

Question 4

Question 0

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Question 0

Time in s	Volume of hydrogen with $1.0\ \mathrm{mol/dm^3}$ acid in $\mathrm{cm^3}$	Volume of hydrogen with $2.0\ \mathrm{mol/dm^3}$ acid in $\mathrm{cm^3}$
0	0	0
20	58	110
40	100	166
60	130	190
80	152	198
100	170	200
120	184	200
140	196	200
160	200	200

Time in s	Volume of hydrogen with $1.0\ \mathrm{mol/dm^3}$ acid in $\mathrm{cm^3}$	Volume of hydrogen with $2.0\ \mathrm{mol/dm^3}$ acid in $\mathrm{cm^3}$
0	0	0
20	58	110
40	100	166
60	130	190
80	152	198
100	170	200
120	184	200
140	196	200
160	200	200

Time in s	Volume of hydrogen with $1.0\ \mathrm{mol/dm^3}$ acid in $\mathrm{cm^3}$	Volume of hydrogen with $2.0\ \mathrm{mol/dm^3}$ acid in $\mathrm{cm^3}$
0	0	0
20	58	110
40	100	166
60	130	190
80	152	198
100	170	200
120	184	200
140	196	200
160	200	200