1. A pupil made the following observations on dripping taps. 45cm3 of water was collected from Tap A in 3 minutes. 340cm3 of water was collected from Tap B in 20 minutes. By calculating the average rate of loss of water from each tap, find out which tap was dripping faster.
2. A farmer records the weight of his pigs every Monday. Here is part of the record for one of the pigs.
Calculate the average rate of weight gain per week:-
i) during the first week ii) during the first three weeks iii) over the five week period
3. A pupil was attempting to measure the rate of a chemical reaction which produced a gas. After six seconds 8cm3 of gas had been collected. After ten seconds the total volume of gas collected was 14cm3. Calculate the average rate of the reaction during this time interval (from six to ten seconds).
4. The graph opposite shows the volume of hydrogen gas released when a 10cm strip of magnesium (mass = 0.1g) was added to 30cm 3 of 1 mol l-1 hydrochloric acid.
(a) Calculate the average rate of reaction
i) over the first 15 seconds
ii) between 20 and 30 seconds
(b) How long did it take for the reaction to stop?
(c) The graph shows that the rate of reaction changes as the reaction proceeds. Explain why it changes in this way.
5. Marble chips (calcium carbonate), reacted with excess dilute hydrochloric acid.
The rate of reaction was followed by recording the mass of the container and the reaction mixture over a period of time. The results of the experiment are shown in the following graph.
(a) Write a balanced equation for the reaction.
(b) Give a reason for the loss of mass of the container.
(c) Calculate the average rate of reaction over the first five minutes.
(d) Why does the average rate of reaction decrease as the reaction proceeds?
6. The results shown below were obtained when 0.42 g of powdered chalk was added to 20cm3 hydrochloric acid, concentration 2 mol l-1 (an excess of the acid).
(a) Sketch the graph and add a solid line to the graph to show what would happen if 0.42g of chalk lumps was used instead of powdered chips.
(b) Add a dotted line to the graph to show what would happen if 20 cm3 of 3 mol l-1 hydrochloric acid was used instead of 2 mol l-1 hydrochloric acid.
7. 1.0 g of zinc was placed in 20 cm3 of 2 mol l-1 hydrochloric acid.
After 20 seconds the zinc was removed, washed, dried and re-weighed.
The remaining zinc weighed 0.35 g.
(a) Write a balanced chemical equation for the reaction.
(b) Calculate the average rate of the reaction.
(c) Calculate the number of moles of hydrochloric acid used up in the 20 seconds.
8. A pupil was investigating the effect of temperature on the rate of a chemical reaction and obtained the following data.
(a) Copy the table and calculate the relative rate of reaction at each temperature and add them to the table, putting the correct units in the brackets.
(b) Plot a graph of relative rate against temperature.
(c) Predict what the relative rate of the reaction will be at 50 0C.
(d) Use the graph to estimate the time for the reaction to finish at 40 0C.
9. (a) Explain
i) Why decreasing the particle size increases the rate of a chemical reaction.
ii) Why increasing the concentration speeds up a chemical reaction.
(b) Give an everyday example of a reaction speeded up by
i) decreasing the particle size
ii) increasing the concentration
10. When hydrochloric acid is added to a solution of sodium thiosulphate the following reaction takes place.
Solid sulphur forms in the solution.
In one set of experiments the effect of varying the concentration of sodium thiosulphate was studied. Some of the volumes of solutions used are shown.
(a) Copy and then complete the table to show the volumes of water and acid that would have been used.
(b) Describe how the reaction time could have been measured.
(c) Describe how the relative rate of reaction would be obtained from each of the results.
11. Hydrogen peroxide can be used to clean contact lenses. In this process, the enzyme catalase is added to break down hydrogen peroxide. The equation for the reaction is:
The rate of oxygen production was measured in three laboratory experiments using the same volume of hydrogen peroxide at the same temperature.
The curve obtained for experiment A is shown.
(a) Calculate the average rate of the reaction over the first 40 s.
(b) Copy the graph and add curves to the graph to show the results of experiments B and C. Label each curve clearly.
12. The graph shows the concentrations of reactant and product as equilibrium is established in a reaction.
(a) Calculate the average rate of reaction over the first 10 s.
(b) The equilibrium constant for a reaction is given the symbol K
In this reaction K is given by:
Calculate the value of K for the reaction.
(c) The reaction is repeated using a homogeneous catalyst.
(i) What is meant by a homogeneous catalyst?
(ii) What effect would the introduction of the catalyst have on the value of K?
13. Excess zinc was added to 100 cm3 of hydrochloric acid, concentration 1 mol l–1. Graph I refers to this reaction.
Graph II could be for…………….
A excess zinc reacting with 100cm3 of hydrochloric acid, concentration 2mol l–1
B. excess zinc reacting with 100cm3 of sulphuric acid, concentration 1 mol l–1
C. excess zinc reacting with 100cm3 of ethanoic acid, concentration 1 mol l–1
D. excess magnesium reacting with 100cm3 of hydrochloric acid, concentration 1 mol l–1.
14. The graph shows how the rate of a reaction varies with the concentration of one of the reactants.
What was the reaction time, in seconds, when the concentration of the reactant was 0.50 mol l–1?
A 0.2
B 0.5
C 2.0
D 5.0
