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Question 1
a) | Describe a test-tube reaction that could be used to distinguish between each of the following pairs of compounds. For each pair, name the reagent(s) required, and the observation that would be made for each compound. |
i) | Butan-1-ol and 2-methylpropan-2-ol
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ii) | Propanoic acid and methyl propanoate
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iii) | Butanone and butanal
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iv) | Propane and 1-chloropropane
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v) | Benzene and cyclohexene
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Question 2
Test-tube reactions can be used to identify the functional groups in organic molecules. You are provided with samples of each of the four compounds. |
a) | Describe a chemical test that would produce a positive result with compounds A and B but a negative result with compounds C and D. You should describe what would be observed in the positive result.
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b) | Describe a chemical test would distinguish compound A from compound B. You should describe what would be observed in the positive result.
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c) | Describe a chemical test that would produce a positive result with compounds C and D but a negative result with compounds A and B. You should describe what would be observed in the positive result.
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d) | Describe a chemical test would distinguish compound C from compound D. You should describe what would be observed in the positive result.
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Question 3
Halogenoalkanes react with water to produce alcohols and halide ions. C4H9X + H2O ➔ C4H9OH + X- + H+ |
Test tube experiments can be carried out to investigate the relative rates of these substitution reactions. The halogenoalkanes 1‐chlorobutane, 1‐bromobutane and 1‐iodobutane can be used. Some of the steps in these experiments are
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State the purpose of adding ethanol to each of the test tubes.
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b) | Give one reason why the test tubes were put in the same beaker of hot water.
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c) | Give one reason why the test tubes were shaken after the addition of aqueous silver nitrate.
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d) | State how the halogen atom present in each halogenoalkane can be identified using observations from this experiment in part a).
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e) | Identify further reagents that can be added, including relevant observations, to confirm the identity of the halogen atom present in each halogenoalkane.
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Question 4
The structures for six naturally occurring organic compounds with pleasant smells, A–F, are shown below. |
a) | Identify the isomer(s) that would react when warmed with acidified potassium dichromate(VI). State the expected observation when acidified potassium dichromate(VI) reacts.
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b) | Identify the isomer(s) that would react with Tollens' reagent. State the expected observation when Tollens' reagent reacts.
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c) | Separate samples of A-F are warmed with ethanoic acid and a few drops of concentrated sulfuric acid. In each case the mixture is then poured into a solution of sodium hydrogencarbonate. Identify the isomer(s) that would react with ethanoic acid.
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d) | Suggest a simple way to detect if the ethanoic acid reacts with each organic compound.
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e) | Give a reason why the mixture is poured into sodium hydrogencarbonate solution.
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Question 5
The following three carbonyl compounds are structural isomers of C5H10O2. |
a) | Describe chemical tests that you could carry out in test-tubes to distinguish between compounds A, B and C. Include appropriate reagents and any relevant observations. Also include equations showing structures for the organic compounds involved.
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b) | Maleic acid is a stereoisomer of fumaric acid. The structure of the two acids are shown below. |
Describe chemical tests that can be carried out in a laboratory to identify the two functional groups in both acids.
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c) | Give the empirical formula of both acids.
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d) | State what type of geometric isomer maleic acid is.
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e) | Explain why maleic acid and fumaric acid are different compounds.
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