CAIE
Chemistry
(9701)
Questions & Answers
On the grid opposite, plot a graph of rate of reaction (y-axis) against volume of FA 1 (x-axis). Include the origin, (0,0), in your scales. Circle any points you consider anomalous and draw a line of best fit.
Use your graph to calculate the time that the reaction would have taken if 5.00 cm3 of FA 1 had been used. Show on the graph how you obtained your answer. time = .............................. s
Using data from Experiments 1 and 2, show by calculation that the volume of aqueous potassium iodide, FA 1, used was directly proportional to the concentration of iodide ions.
Explain, by referring to your graph or your table of results, how the rate of reaction is affected by an increase in the concentration of aqueous potassium iodide, FA 1.
Write an ionic equation for the reaction between thiosulfate ions and hydrogen ions in aqueous solution. Include state symbols.
A student carries out the same investigation as in (a) but the solutions are mixed in a different order. The student places FA 1 and an appropriate volume of distilled water in one beaker and all the other reactants in a second beaker. The student then transfers the mixture from the second beaker to the first and starts timing. Tick the box for the statement you consider correct. Explain your answer. The student's method is better than that in (a). The two methods are equally good. The student's method is not as good as that in (a). reason
Another student investigates the effect of iron(III) concentration on the rate of this reaction. The student carries out another experiment, Experiment 6, and the rate is compared to that of Experiment 2. In Experiment 2, the volumes used were: reagent volume / cm3 FA 1 10.00 FA 2 10.0 FA 3 20.0 FA 4 10.0 distilled water 10.00 Suggest the volumes the student could use for Experiment 6.
This student records a time of 178 s for Experiment 2. The rate of reaction is directly proportional to the concentration of iron(III) ions. Suggest how long it would take the reaction mixture proposed for Experiment 6 in (f)(i) to turn blue-black. Assume that Experiment 6 is carried out at the same temperature as Experiment 2. Do not carry out Experiment 6. time = .............................. s
FA 5 is a salt consisting of two ions both of which are listed in the Qualitative Analysis Notes. Place a small spatula measure of FA 5 into a hard-glass test-tube. Heat the tube gently at first and then more strongly. Record all your observations.
FA 6 is a sample of the residue obtained from FA 5 after strong heating. Place a small spatula measure of FA 6 in a test-tube and add a 1 cm depth of aqueous hydrogen peroxide. Record your observations.
Dissolve a spatula measure of FA 5 in a 5 cm depth of distilled water in a boiling tube. Use separate 1 cm depths of this solution in test-tubes for the following tests. Record your observations. Keep the remainder of FA 5(aq) for use in 2(b)(ii). Test 1 Add aqueous sodium hydroxide. Test 2 Add a 1 cm depth of aqueous hydrogen peroxide, then add aqueous sodium hydroxide.
FA 7 is a solution of a different salt. The cation present in FA 7 is not listed in the Qualitative Analysis Notes. FA 5(aq) and FA 7 each contain either a halide ion or an anion containing sulfur. These anions are listed in the Qualitative Analysis Notes. For both of these anions, select reagents that you would use in order to carry out tests that give positive results. Record the reagents and the ions for which they would test.
Carry out both of your tests on FA 5(aq) and FA 7 and record your results in the space below.
Use your observations in (a) and (b)(ii) to identify the ions present in FA 5 and FA 7. Write the formula of each ion in the table. If the tests you carry out do not allow you to identify any of the ions, write 'unknown'. FA 5 FA 7 cation anion
Suggest what you would observe if you added aqueous chlorine to separate portions of aqueous solutions of FA 5 and FA 7. Do not carry out this test. aqueous chlorine and FA 5(aq) aqueous chlorine and FA 7(aq)