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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level
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*4752941019*
CHEMISTRY Advanced Practical Skills 2
9701/32 May/June 2012 2 hours
Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions
READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Give details of the practical session and laboratory where appropriate, in the boxes provided. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. You may lose marks if you do not show your working or if you do not use appropriate units. Use of a Data Booklet is unnecessary. Qualitative Analysis Notes are printed on pages 11 and 12. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. Session
Laboratory
For Examiner’s Use 1 2 Total This document consists of 12 printed pages.
IB12 06_9701_32/5RP © UCLES 2012
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2 1 Iodide ions are oxidised by iron(III) ions in the presence of acid. 2Fe3+(aq) + 2I–(aq) → 2Fe2+(aq) + I2(aq) The rate of this reaction can be measured by adding thiosulfate ions, S2O32–, and some starch indicator to the mixture. As the iodine is produced, it reacts immediately with the thiosulfate ions and is reduced back to iodide ions. I2(aq) + 2S2O32–(aq) → 2I–(aq) + S4O62–(aq) When all the thiosulfate ions have reacted, the iodine which continues to be produced then turns the starch indicator blue-black. The rate of reaction may be determined by timing how long it takes for the reaction mixture to turn blue-black. You are to investigate how the rate of reaction is affected by changing the concentration of the reagents. FB 1 is 0.0500 mol dm–3 aqueous acidified iron(III) chloride, FeCl 3. FB 2 is 0.0500 mol dm–3 aqueous potassium iodide, KI. FB 3 is 0.00500 mol dm–3 aqueous sodium thiosulfate, Na2S2O3. FB 4 is starch indicator. Read through the instructions carefully and prepare a table for your results on page 3 before starting any practical work. (a) Method Experiment 1 ● Using a 25 cm3 measuring cylinder add the following to a 100 cm3 beaker: ○ 10 cm3 of FB 2 ○ 20 cm3 of FB 3 ○ 10 cm3 of FB 4 ● Fill the burette labelled FB 1 with aqueous acidified iron(III) chloride, FB 1.
The Essay on Answers The Question Poem Dark Black
The poem 'Telephone conversation' is staged by a black man who is looking for a flat but ends up phoning to a landlady who is racist but tries to be polite in finding out whether he is he is a dark or light one. When he first speaks to her he feels awkward as he feels he has to confess that he is African. Also I think he feels as though he has been in the same position before somewhere else and he ...
● Run 20.00 cm3 of FB 1 into a second 100 cm3 beaker. ● Add the contents of the first beaker to the second beaker and start timing immediately. ● Stir the mixture once and place the beaker on a white tile. ● Stop timing as soon as the solution turns blue-black. ● Record this reaction time to the nearest second in the table that you have prepared on page 3. ● Wash out both beakers. Experiment 2 ● Using a 25 cm3 measuring cylinder add the following to a 100 cm3 beaker: ○ 10 cm3 of FB 2 ○ 20 cm3 of FB 3 ○ 10 cm3 of FB 4 ● Fill a second burette with distilled water. ● Run 10.00 cm3 of FB 1 into a second 100 cm3 beaker. ● Run 10.00 cm3 of distilled water into the beaker containing FB 1. ● Add the contents of the first beaker to the second beaker and start timing immediately. ● Stir the mixture once and place the beaker on a white tile. ● Stop timing as soon as the solution turns blue-black. ● Record this reaction time to the nearest second in the table that you have prepared on page 3. ● Wash out both beakers.
The Coursework on Rate Of Reaction Time Experiment Moles
Rate of Reaction Aim: To find out how different concentrations change the rate of reaction Theory: In this experiment the collision theory is in use. It means that when the concentrates solutions of hydrochloric acid is use, more particles are found in the same space, which means they are more likely to collide with each other. the more the concentrated the solution, the more of the collisions ...
© UCLES 2012 9701/32/M/J/12 For Examiner’s Use
3 Experiments 3 – 5 ● Carry out three further experiments to investigate how the reaction time changes with different volumes of iron(III) chloride. Remember that the combined volume of FB 1 and distilled water must always be 20.00 cm3. Do not use a volume of FB 1 that is less than 6.00 cm3. Record all your results in a single table. You should include the volume of iron(III) chloride, the volume of distilled water and the reaction time.
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[9] (b) In order to convert the times measured in the experiments into rates of reaction, it is necessary first to work out the change in the iron(III) ion concentration that occurs from the time when the mixtures are combined to the time when the solution turns blue-black. You must show your working. (i) Calculate how many moles of thiosulfate ions, S2O32–, are added in each experiment.
moles of S2O32– = …………….. mol (ii) Calculate how many moles of iodine, I2, reacted with the number of moles of thiosulfate ions calculated in (i).
moles of I2 = …………….. mol (iii) Calculate how many moles of iron(III) ions, Fe3+, reacted to form the number of moles of iodine calculated in (ii).
moles of Fe3+ = …………….. mol (iv) Use your answer from (iii) to calculate the decrease in concentration of iron(III) ions in the total reaction mixture (60 cm3) from the start of the experiment to the point when the solution turned blue-black.
decrease in Fe3+ concentration = …………….. mol dm–3 [3]
© UCLES 2012 9701/32/M/J/12
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4 (c) The rate of the reaction can be represented by the following formula. ‘rate’ = decrease in Fe3+ concentration from (b)(iv) × 106 reaction time
For Examiner’s Use
Use your experimental results to complete the following table. Include the volume of FB 1, the reaction time and the ‘rate’ with their units. If you were unable to answer (b)(iv), you may assume that the decrease in Fe3+ concentration is 2.25 × 10–3 mol dm–3 (This is not the correct value).
The Essay on The effect o temperature on a Reaction time
Abstract: This project looks at how the temperature of an experiment can affect its reaction time. The purpose of this experiment is to determine if dissolving reactions are affected by waters temperature. I believe that if the H2O temperature increases, then the Alka-Seltzer tablet will dissolve faster because the hot water molecules will move faster colliding with the tablet particles. Water ...
[2]
(d) On the grid opposite, plot ‘rate’ against the volume of FB 1. Draw a line of best fit.
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5
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6 (e) In your experiments, the volume of FB 1 represents the concentration of iron(III) chloride. From your results, what conclusion can you draw about the relationship between the rate of reaction and the concentration of iron(III) chloride? …………………………………………………………………………………………………………………………. …………………………………………………………………………………………………………………………. …………………………………………………………………………………………………………………………. ……………………………………………………………………………………………………………………. [2]
For Examiner’s Use
(f) One source of error in this experiment arises from measuring the volumes of solutions. (i) Calculate the maximum percentage error in the volume of FB 1 used in Experiment 1.
maximum percentage error = …………………% (ii) Other than errors involving measurements of volumes, suggest an additional source of error in these experiments. …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… (iii) In this experiment, thiosulfate ions reduce iodine while iron(III) ions oxidise iodide ions. What other reaction might take place that would affect your confidence in the conclusions you made in (e)? …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… [4]
The Essay on Flame test lab report
Intro: The flame test is a procedure used by chemists to identify the presence of specified metal ions, based on the color the flame that appears along with it when it’s heated. Our flame test was in lab class, where the main aim was to tested different solid metals in the flame in order to observe the wide variety of colors those chemicals also sometimes compounds (by mixing them) they ...
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7 (g) (i) Carry out one additional experiment using the following volumes of each reagent. Use the same method as in (a), mix FB 2, FB 3 and FB 4 together and start the reaction by adding this mixture to FB 1 and the distilled water. ○ ○ ○ ○ ○ 10.00 cm3 of FB 1 20.00 cm3 of distilled water 10 cm3 of FB 2 10 cm3 of FB 3 10 cm3 of FB 4
For Examiner’s Use
Record the time for the reaction to go blue-black.
(ii) Explain the relationship between this time and the one you recorded in Experiment 2. …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… [2] [Total: 26]
The Essay on White Precipitate Ions Add Presence
Anions and cations can be identified using a variety of chemical tests. Because some ions produce similar results with one test, other confirmatory tests are essential. ANIONS CARBONATE IONS - add dilute nitric acid If the mixture effervesces (releases CO 2 gas), carbonate ions are present. To test that it is CO 2 gas, preform a limewater test. CO 32- + 2 H+ H 2 CO 3 (s) To confirm the ...
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8 2 Qualitative Analysis At each stage in any test you are to record details of the following. ● ● ● colour changes seen the formation of any precipitate the solubility of such precipitates in an excess of the reagent added
For Examiner’s Use
Where gases are released they should be identified by a test, described in the appropriate place in your observations. You should indicate clearly at what stage in a test a change occurs. Marks are not given for chemical equations. No additional tests for ions present should be attempted. If any solution is warmed, a boiling tube MUST be used. Rinse and reuse test-tubes and boiling tubes where possible. Where reagents are selected for use in a test, the full name or correct formula of the reagents must be given.
(a) FB 5, FB 6, FB 7 and FB 8 are aqueous solutions each of which contains a single cation and a single anion. Some of the ions present are listed below. Pb2+ Ba2+ H+ CrO42– SO42– Cl –
By observing the reactions that occur when pairs of the solutions are mixed together, you will be able to identify which solution contains which of these ions.
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9 Use 1 cm depth of each solution in a test-tube and record your observations in the following table. FB 6 FB 7 FB 8
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The Term Paper on Flow Chart Precipitate Ions Unknown
Qualitative analysis is used in the determination of the identity of a substance. It is different from quantitative analysis, which deals with the determination of the amount of a substance. In this experiment, qualitative analysis techniques are used to determine whether or not a sample contains a certain ion. When using this method, an unknown and a reactant are mixed. The result of the reaction ...
FB 5
FB 6
I II
FB 7
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(b) From your observations, deduce which solution contains each of the following ions.
I
ion solution
Pb2+
Ba2+
H+
CrO42–
SO42–
Cl –
II III
[3]
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10 (c) The anion in FB 9 is either the nitrite ion, NO2–, or the nitrate ion, NO3–. (i) Describe a test you could carry out that would give positive results for both of these ions. …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… (ii) Describe a test you could carry out that would distinguish between these two ions. …………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………… (iii) Carry out both of these tests and record your results in an appropriate form in the space below.
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(iv) Which anion is present in FB 9? …………………………………………….. [6] [Total: 14]
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11 Qualitative Analysis Notes Key: [ppt. = precipitate] 1 Reactions of aqueous cations reaction with NaOH(aq) white ppt. soluble in excess no ppt. ammonia produced on heating no ppt. (if reagents are pure) NH3(aq) white ppt. insoluble in excess –
ion aluminium, Al 3+(aq) ammonium, NH4+(aq) barium, Ba2+(aq) calcium, Ca2+(aq) chromium(III), Cr3+(aq) copper(II), Cu2+(aq) iron(II), Fe2+(aq) iron(III), Fe3+(aq) lead(II), Pb2+(aq) magnesium, Mg2+(aq) manganese(II), Mn2+(aq) zinc, Zn2+(aq)
no ppt.
white ppt. with high [Ca2+(aq)] grey-green ppt. soluble in excess giving dark green solution pale blue ppt. insoluble in excess green ppt. turning brown on contact with air insoluble in excess red-brown ppt. insoluble in excess white ppt. soluble in excess white ppt. insoluble in excess off-white ppt. rapidly turning brown on contact with air insoluble in excess white ppt. soluble in excess
no ppt. grey-green ppt. insoluble in excess blue ppt. soluble in excess giving dark blue solution green ppt. turning brown on contact with air insoluble in excess red-brown ppt. insoluble in excess white ppt. insoluble in excess white ppt. insoluble in excess off-white ppt. rapidly turning brown on contact with air insoluble in excess white ppt. soluble in excess
[Lead(II) ions can be distinguished from aluminium ions by the insolubility of lead(II) chloride.]
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12 2 Reactions of anions ion carbonate, CO3
2–
reaction CO2 liberated by dilute acids yellow solution turns orange with H+(aq); gives yellow ppt. with Ba2+(aq); gives bright yellow ppt. with Pb2+(aq) gives white ppt. with Ag+(aq) (soluble in NH3(aq)); gives white ppt. with Pb2+(aq) gives cream ppt. with Ag+(aq) (partially soluble in NH3(aq)); gives white ppt. with Pb2+(aq) gives yellow ppt. with Ag+(aq) (insoluble in NH3(aq)); gives yellow ppt. with Pb2+(aq) NH3 liberated on heating with OH–(aq) and Al foil NH3 liberated on heating with OH–(aq) and Al foil; NO liberated by dilute acids (colourless NO → (pale) brown NO2 in air) gives white ppt. with Ba2+(aq) or with Pb2+(aq) (insoluble in excess dilute strong acids) SO2 liberated with dilute acids; gives white ppt. with Ba2+(aq) (soluble in excess dilute strong acids)
chromate(VI), CrO42–(aq) chloride, Cl –(aq) bromide, Br (aq) iodide, I (aq)
– –
nitrate, NO3–(aq) nitrite, NO2–(aq) sulfate, SO42–(aq) sulfite, SO3 (aq)
2–
3
Tests for gases gas test and test result turns damp red litmus paper blue gives a white ppt. with limewater (ppt. dissolves with excess CO2) bleaches damp litmus paper “pops” with a lighted splint relights a glowing splint turns acidified aqueous potassium dichromate(VI) from orange to green
ammonia, NH3 carbon dioxide, CO2 chlorine, Cl 2 hydrogen, H2 oxygen, O2 sulfur dioxide, SO2
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