Name: Rate of reaction. Class: Foundation revision questions. Date: 47 minutes. Time: 46 marks. Marks: Comments: Page 1 of 21

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1 Rate of reaction Foundation revision questions Name: Class: Date: Time: 47 minutes Marks: 46 marks Comments: Page of 2

2 (a) The figure below represents the reaction of sulfur dioxide with oxygen. Oxygen Sulfur dioxide Sulfur trioxide (i) Complete the word equation for the reaction of sulfur dioxide with oxygen. sulfur dioxide + () (ii) Draw a ring around the correct answer to complete the sentence. a compound. Sulfur dioxide (SO 2 ) is an element. a mixture. () (b) The reactants are gases. When the pressure of the gases is increased, the reaction gets faster. Complete the sentence. When the pressure of the gases is increased, the frequency of the collisions. () (c) The particles need energy to react. Complete the sentence. The minimum amount of energy that particles need to react is called the energy. () (d) Give one way of increasing the rate of the reaction other than changing the pressure. () (Total 5 marks) Page 2 of 2

3 2 The picture shows three glowsticks. Photograph supplied by istockphoto/thinktsock Glow sticks contain several chemicals. When a glow stick is bent the chemicals mix. A chemical reaction takes place which causes light to be given out. A student investigated three glow sticks. One was placed in water at 5 C, one in water at 40 C and one in water at 70 C. The results are shown in the table. Effect on glow stick Temperature in C Brightness of light Time it gave out light, in hours 5 dim 7 40 bright 3 70 very bright (a) How did increasing the temperature affect the brightness of the glow stick? () (b) How did increasing the temperature affect the time it gave out light? () Page 3 of 2

4 (c) The student was asked why an increase in temperature changes the rate of the chemical reaction. The student listed five ideas. Only three of them are correct. Put ticks ( ) next to the three correct ideas. Ideas Ticks ( ) The particles will collide more often. The particles will be more concentrated. The particles will move faster. The particles will have more energy. The particles will get bigger. (3) (d) Suggest one way the student could improve this investigation. () (Total 6 marks) Page 4 of 2

5 3 Pieces of zinc react with dilute acid to form hydrogen gas. The graph shows how the volume of hydrogen gas produced changes with time. (a) Describe, as fully as you can, how the volume of gas produced changes with time. (2) (b) A student wants to make the reaction take place faster. Some suggestions are given in the table. Put ticks ( ) next to the two suggestions that would make the reaction take place faster. Suggestions ( ) Use bigger pieces of zinc. Use a more concentrated acid. Use zinc powder. Decrease the temperature of the acid. (2) (Total 4 marks) Page 5 of 2

6 4 A student investigated the rate of the reaction between magnesium and dilute hydrochloric acid. The student used the apparatus shown in Figure to collect the gas produced. Figure (a) Outline a plan to investigate how the rate of this reaction changed when the concentration of the hydrochloric acid was changed. Describe how you would do the investigation and the measurements you would make. Describe how you would make it a fair test. You do not need to write about safety precautions. (6) Page 6 of 2

7 (b) Figure 2 shows the gas syringe during one of the experiments. Figure 2 What is the volume of gas collected? Tick one box. 5.3 cm cm cm cm 3 () Page 7 of 2

8 (c) Figure 3 shows the student s results for one concentration of hydrochloric acid. Figure 3 The table below shows the student s results when the concentration was two times greater than the results on Figure 3 Time in seconds Volume of gas produced in cm Plot the results in the table above on the grid in Figure 3. Draw a line of best fit. (3) Page 8 of 2

9 (d) Give one conclusion about how the rate of reaction changed when the concentration of hydrochloric acid was changed. () (Total marks) 5 A student investigated the rate of reaction between sodium thiosulfate solution and dilute hydrochloric acid, as shown in Figure. The reaction produced a precipitate, which made the mixture turn cloudy. The student timed how long it took until she could no longer see the cross. She calculated the rate of the reaction. (a) The equation for the reaction is: Na 2 S 2 O 3 (aq) + 2 HCl(aq) 2 NaCl(aq) + S(s) + SO 2 (g) + H 2 O(l) Name the product that made the mixture go cloudy. () Page 9 of 2

10 (b) The student investigated the effect of changing the temperature of the sodium thiosulfate solution on the rate of reaction. She plotted her results on a graph, as shown in Figure 2. Describe the trends shown in the student s results. (2) Page 0 of 2

11 (c) The student then investigated the effect of changing the concentration of sodium thiosulfate solution on the rate of the reaction. (i) Suggest two variables the student would need to control to make sure that her results were valid. (2) (ii) From this investigation the student correctly concluded: As the concentration of sodium thiosulfate solution doubles, the rate of reaction doubles. Explain the student s conclusion in terms of particles. (3) (Total 8 marks) Page of 2

12 6 A student investigated the rate of reaction between calcium carbonate (marble chips) and hydrochloric acid. The student used the apparatus shown in Figure. The student: recorded the volume of gas collected every 5 seconds repeated the experiment using hydrochloric acid at different temperatures. The equation for the reaction is: CaCO 3 (s) + 2 HCl(aq) CaCl 2 (aq) + H 2 O(l) + CO 2 (g) Page 2 of 2

13 (a) The student plotted results for the hydrochloric acid at 20 C and 40 C on a graph. Figure 2 shows the student s graph. Use information from Figure 2 to answer these questions. (i) State one conclusion the student could make about the effect of temperature on the rate of the reaction. () (ii) Give one reason why the student could make this conclusion. () (iii) For the hydrochloric acid at 60 C the student had collected 30 cm 3 after 5 seconds. Calculate the average rate of reaction from 0 to 5 seconds. Rate of reaction = cm 3 per second () Page 3 of 2

14 (b) The student then investigated how the surface area of marble chips affected the rate of reaction. (i) Which two variables should the student keep constant? Tick ( ) two boxes. Amount of water in the trough Concentration of acid Mass of marble chips Size of marble chips Volume of measuring cylinder (2) (ii) Explain, in terms of particles and collisions, the effect that increasing the surface area of the marble chips has on the rate of reaction. (2) (c) Calcium carbonate is a catalyst for the industrial production of biodiesel. Give one reason why using a catalyst reduces costs. () (Total 8 marks) Page 4 of 2

15 7 This label was on a bottle of stain remover. When Simply Amazing is mixed with water a reaction takes place which produces bubbles of oxygen gas. (i) Suggest a method that you could use to measure how quickly this reaction takes place. (2) (ii) Read the instructions on the label and then suggest how increasing the temperature of the water affects the rate of this reaction. () Page 5 of 2

16 (iii) Suggest one other way in which the rate of a reaction can be changed. () (Total 4 marks) Page 6 of 2

17 Mark schemes (a) (i) oxygen, sulfur trioxide both needed for mark (ii) compound (b) increases accept (goes) higher / (goes) up / (is) faster) / (are) more frequent (c) activation (d) catalyst or increase temperature [5] 2 (a) the glow stick is brighter (owtte) accept glow stick is less bright at low temperatures (owtte) ignore references to rate / particles (b) gave out light for less time accept use of figures from table for comparison allow reference to speed / rate eg quicker / faster reaction (c) the particles will collide more often the particles will move faster the particles will have more energy (d) any one from: repeat allow more glow sticks measure brightness eg use light meter more temperatures or wider range improve precision [6] Page 7 of 2

18 3 (a) any two from: increases owtte allow goes up until reaches maximum / levels off owtte quickly at first owtte then more slowly / rate decreases allow reaction finished ignore rate increases 2 (b) use a more concentrated acid list principle applies use zinc powder 2 [4] 4 (a) Level 3 (5 6 marks): A coherent method is described with relevant detail, which demonstrates a broad understanding of the relevant scientific techniques and procedures. The steps in the method are logically ordered with the dependent and control variables correctly identified. The method would lead to the production of valid results. Level 2 (3 4 marks): The bulk of a method is described with mostly relevant detail, which demonstrates a reasonable understanding of the relevant scientific techniques and procedures. The method may not be in a completely logical sequence and may be missing some detail. Level ( 2 marks): Simple statements are made which demonstrate some understanding of some of the relevant scientific techniques and procedures. The response may lack a logical structure and would not lead to the production of valid results. 0 marks: No relevant content Indicative content remove bung and add magnesium start stopclock / timer measure volume of gas at fixed time intervals repeat with different concentrations of acid control volume of acid control initial temperature of acid control amount / mass / length / particle size of magnesium 6 Page 8 of 2

19 (b) 6.5 cm 3 (c) all points plotted correctly allow mark for 4 points plotted correctly 2 best fit straight line drawn (d) when the concentration of acid increased the rate of reaction increased or vice versa answer must use the terms rate of reaction linked to concentration [] 5 (a) sulfur / sulphur / S / S(s) (b) as the temperature increases, the rate of reaction increases allow two correct values for rate quoted (from graph) at different temperatures the rate of increase increases or there is an exponential relationship accept the rate of reaction increases slowly (from 20 C to 50 C) then increases more rapidly for 2 marks answer MUST be based on rate / speed of reaction (c) (i) any two from: temperature (of the reactants) concentration of hydrochloric acid volume of hydrochloric acid volume of sodium thiosulfate the (size / darkness / thickness of the) cross total volume of solution. if no other marks gained, allow mark for: rate of stirring OR amount of hydrochloric acid / sodium thiosulfate OR volume of solution 2 Page 9 of 2

20 (ii) (because as the concentration increases) the number of particles per unit volume increases or particles are closer together. idea of more particles in a given space is required for the first mark. ignore references to area. (therefore) the frequency of (successful) collisions increases allow increased chance / probability of collisions number of collisions increases is insufficient here. must mention per unit time or frequency. ignore speed of collisions. if reference to space and time missing from M and M2 but they are otherwise correct, then award mark. so the number of particles (per unit volume) doubles or (the frequency of) collisions doubles. students can score 2 marks for a qualitative explanation; the third mark is for a quantitative explanation. [8] 6 (a) (i) the higher the temperature, the greater the rate or at 40 C rate is faster than at 20 C accept the higher the temperature, the faster the reaction (ii) 40 C curve is steeper accept the 40 C line becomes horizontal sooner accept at higher temperatures the reaction finishes sooner accept reaction finishes sooner at 40 C accept at higher temperatures the gas is produced faster or correct comparison of data from the graph (iii) 2 Page 20 of 2

21 (b) (i) Concentration of acid Mass of marble chips 2 (ii) increases rate incorrect reference to energy = max (because of) more frequent collisions (between particles) accept particles are more likely to collide ignore more collisions ignore more successful collisions (c) any one from: increases rate of reaction reduces energy required lower temperature can be used catalyst is not used up. [8] 7 (i) measure volume / mass of gas produced in a certain time period mark is for a sensible way of measuring the amount of product produced and mark is for the idea of timing e.g. measure volume of gas produced at regular time intervals or time taken to fill a test tube with the gas or collect a certain volume of gas (measuring the rate at which bubbles are produced e.g. number of bubbles in 30 seconds gains only mark unless an enclosed system is used) or measure decrease in mass of flask and contents at regular time intervals or time taken for the mass to decrease by certain amount (ii) increases rate (owtte) (ii) change the concentration or add a catalyst or change the surface area or lower the temperature accept expose to sunlight (owtte) or change the amount of water / powder / solution used ignore stirring [4] Page 2 of 2