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The rate of reaction can be calculated as shown.
$$\text{rate} = \frac{1000}{\text{reaction time}}$$
Calculate the rate of reaction for each experiment and include this in your table.
(b) Plot a graph of rate (y-axis) against average temperature (x-axis) on the grid opposite. Select a scale on the x-axis to include an average temperature of 15.0°C. Label any points you consider anomalous.
Draw a line of best fit and extrapolate it to 15.0°C. [4]
(c) Use your graph to calculate the time to the nearest second that the reaction would have taken if the average temperature had been 52.5°C. Show on the grid how you obtained your answer.
time = ......................... s [2]
(d) Explain, by referring to your graph or your table of results, how the rate of reaction is affected by an increase in temperature.
.................................................................................................................................................................................................................................................................. [2]
(e) (i) Calculate the concentration of glucose in $\text{FB 3}$ in $\text{mol⋅dm}^{−3}$.
$\text{concentration of glucose in FB 3} = \text{........................... mol⋅dm}^{−3}$ [1]
(ii) Under certain conditions, 1.0 mole of acidified potassium manganate(VII), $\text{KMnO}_4$, can oxidize 2.5 moles of glucose.
Calculate the volume of $0.010\text{ mol⋅dm}^{−3}$ acidified $\text{KMnO}_4$ that would react with all the glucose present in $25.0 \text{ cm}^3$ of $\text{FB 3}$.
(iii) The formula of glucose can be written as $\text{CHO(CHOH)}_4\text{CH}_2\text{OH}$.
Suggest the formula of an organic product of the oxidation of glucose.
................................................................................................................................. [1]
(f) (i) Calculate the maximum percentage error in the reaction time recorded for Experiment 1. Assume the error of the timer is $\pm 1\text{ s}$.
$\text{maximum percentage error in Experiment 1} = \text{...........................%}$ [1]
(ii) You have carried out experiments at five different temperatures.
Identify an experiment, if any, you should have repeated. Give a reason for your answer.
.................................................................................................................................................................................................................................................................. [1]
(g) Suggest two ways to improve the accuracy of the results for this investigation.
1 ..................................................................................................................................................................................................................................................................
2 .................................................................................................................................................................................................................................................................. [2]
526
509
503
Sandell’s solution reacts in a similar way to Fehling’s reagent.
You will need to heat Sandell’s solution in a hot water bath when using it in tests.
Half fill the 250 cm3 beaker with water and place it on the tripod and gauze. Heat the water until it is boiling then turn off the Bunsen burner. This will be your hot water bath.
(a) FB 4, FB 5 and FB 6 are all solutions of carbohydrates.
• Sugars and starch are carbohydrates.
• Some sugars contain an aldehyde group so act as reducing agents.
• Other sugars do not contain an aldehyde group.
(i) For each test use a 1 cm depth of the solution in a test-tube. Record all your observations in the table.
[Table_1]
Test:
1. Add 2 or 3 drops of aqueous iodine.
2. Add 2 or 3 drops of acidified potassium manganate(VII) and allow to stand for two minutes.
3. Add a 3 cm depth of Sandell’s solution and place the tube in the hot water bath for two minutes.
(ii) Circle the carbohydrate that could be starch.
FB 4 FB 5 FB 6
Circle the carbohydrate that contains an aldehyde group.
FB 4 FB 5 FB 6
(iii) Suggest a different test, other than using Fehling’s reagent, that could be carried out to identify the presence of an aldehyde group. State the reagent(s) you would use and the expected observation if the result were positive.
Do not carry out your test.
Reagent(s): ........................................................
Observation: ........................................................
(b) (i) FB 7 and FB 8 are two of the components of Sandell’s solution. Each contains one cation and one anion. Two of the ions are listed in the Qualitative Analysis Notes.
For each test use a 1 cm depth of solution in a test-tube. Record all your observations in the table.
[Table_2]
Test:
1. Add a few drops of aqueous silver nitrate.
2. Add a few drops of aqueous barium nitrate or aqueous barium chloride, then add dilute nitric acid.
3. Add a few drops of aqueous iodine.
4. Add a 1 cm depth of aqueous iron(II) sulfate.
5. Add a 1 cm depth of FB 8.
(ii) Identify the ions in FB 7 and FB 8. If you are unable to identify any of the ions, write ‘unknown’.
FB 7 cation ................ anion ................
FB 8 cation ................ anion ................
(iii) Write an ionic equation for any reaction in (i) that produced a precipitate. Include state symbols.
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525
545
504
