A LevelChemistryOCRExam Questions1. Development of Practical Skills in Chemistry1.3 Further Organic & Inorganic Chemistry Practicals

Further Organic & Inorganic Chemistry Practicals (OCR A Level Chemistry)

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11 mark

An electrochemical cell is established using the half cells described.

Oxidation half-cell

Reduction half-cell

Silver electrode in 1.0 mol dm-3 silver(II) nitrate solution

Copper electrode in 1.0 mol dm-3 copper(II) sulfate solution

Which chemical is a suitable choice for the salt bridge to connect the electrochemical cell without reacting with either half-cell?

  • Barium chloride

  • Potassium chloride

  • Potassium nitrate

  • Barium nitrate

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21 mark

Which of these statements about the recrystallisation of an organic solid is correct?

  • Recrystallisation decreases the purity of the solid

  • Recrystallisation lowers the melting point of the solid

  • Recrystallisation decreases the yield of an organic product

  • Recrystallisation is a chemical process

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31 mark

Which of the following is true about aldehydes and ketones?

  • Only aldehydes can be identified using Tollens’ reagent

  • Aldehydes and ketones can be identified using Tollens’ reagent

  • Aldehydes are positional isomers of ketones

  • Aldehydes are oxidising agents and ketones are reducing agents

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41 mark

A number of experimental steps are followed during the preparation and purification of aspirin and benzoic acid.

Which of the following does not have the correct pair of experimental steps and reason for the step?

  Experimental step Reason
A

Dissolve the impure compound in a minimum volume of hot solvent

To obtain a saturated solution 
B

Dissolve the impure compound in a minimum volume of hot solvent

To enable crystallisation on cooling
C Hot filter solution through filter paper quickly To remove any soluble impurities
D Hot filter solution through filter paper quickly To prevent crystals from forming during filtration

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    51 mark

    Which set of reagents and results are not the correct tests for different functional groups?

      Functional group(s) Reagent Result
    A Carbonyl 2,4-DNP Orange precipitate formed
    B Carboxylic acid Sodium carbonate solution Effervescence of CO2 evolved
    C 1o and 2o alcohols Sodium dichromate and sulfuric acid Orange to green colour change
    D Haloalkane Warm with aqueous silver nitrate in ethanol Slow formation of white precipitate

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      11 mark

      Which practical technique would be most suitable for purifying a sample of benzoic acid (mp = 122 oC)?

      • Buchner filtration

      • Recrystallisation

      • Using a separating funnel

      • Simple distillation

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      21 mark

      Which of the following is not true about melting point tests?

      • The melting point tubes must be heated slowly

      • High melting point organic solids can decompose before melting

      • The solid must be totally dry and finely powdered

      • Impurities can lower or raise the melting point of organic solids

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      31 mark

      When a Tollens’ test is carried out on propanal, what are the products of the reaction?

      • CH3CH3COOH + Ag

      • CH3CH3CH2OH + Ag

      • CH3CH3COOH + Ag+

      • CH3CH3CH2OH + Ag+

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      41 mark

      Methyl 3-nitrobenzoate can be identified by which laboratory technique(s)?

       

      TLC

      Melting point test

      A

      		 ✓

      		✓

      B

      		 ✓

      		x

      C

      		 x

      		✓

      D

      		 x

      		x

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        5
        Sme Calculator        1 mark

        The EMF of an electrochemical cell can be measured using the following apparatus:

        ocr-1-3m-q5-image


        Which of the following is true?

        • Electrons flow through the external circuit from copper to zinc

        • Sulfate ions flow from the zinc half cell to the copper half cell

        • Zinc is reduced when current flows through the cell

        • Cations and anions flow through the sodium chloride solution in opposite directions

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        11 mark

        Which statement about the preparation of aspirin is correct?

        • In recrystallisation, a large volume of hot solvent must be used to ensure all aspirin and impurities dissolve. 

        • Recrystallisation can be repeated many times to increase the yield of aspirin.  

        • Ethanoyl chloride is preferentially used because it is more reactive than ethanoic anhydride. 

        • Hot filtration is used to keep the aspirin in solution and remove impurities. 

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        21 mark

        Which statement about the preparation of benzoic acid is correct?

        • Benzoic acid is an optically active compound that would turn bromine water colourless. 

        • Benzoic acid has a very small value for Ka.

        • Benzoic acid can be made from benzaldehyde and NaBH4.

        • The purity of benzoic acid is tested with a Thiele tube to reach the melting point more quickly.

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        31 mark

        Which statements about the preparation of methyl 3-nitrobenzoate is/are correct?

        1. Thin layer chromatography can be used to investigate the purity of the product by comparing Rf values before and after recrystallisation.
        2. The reaction mixture must be kept below 6oC to achieve the best yield because nitration is an exothermic reaction.
        3. Insoluble impurities are removed by recrystallisation with hot water as the solvent.

        • 1, 2 and 3

        • Only 1 and 2

        • Only 2 and 3

        • Only 1

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        41 mark

        The molecule below reacted with hydrogen cyanide in a nucleophilic addition reaction. The product was gently warmed with acidified potassium manganate(VII).

        aLbAJQmz_ocr-a2-1-3h-mcq-q4-reactant

        The following tests were carried out on the final product.

        1. Tollens’ reagent.
        2. 2,4-DNPH.
        3. Plane-polarised light.
        4. Acidified potassium dichromate(VI).

        Which row shows the correct results for the tests completed on the final product?

         

        Test 1 result

        Test 2 result

        Test 3 result

        Test 4 result

        A

        Silver mirror

        Orange solution

        No effect

        Orange solution

        B

        Silver mirror

        Deep orange precipitate

        90o rotation

        Green solution

        C

        Colourless solution

        Deep orange precipitate

        No effect

        Orange solution

        D

        Colourless solution

        Orange solution

        90o rotation

        Green solution

         

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          51 mark

          Below are some standard electrode potentials.

          Half equation at electrode

          Electrode potential (V)

          Br2 + 2e- → 2Br-

          +1.07

          Cl2 +2e- → 2Cl-

          +1.36

          F2 +2e- → 2F-

          +2.87

          4H2O +4e- → 4OH- +2H2

          -0.83

          I2 +2e- → 2I-

          +0.54

          SO42- + 4H+ + 2e- → SO2 + 2H2O

          +0.17

          Which statements is/are correct?

          1. The halide ion that is the weakest oxidising agent is iodide.
          2. The salt bridge is soaked in KNO3 to maintain neutrality in the half cells.
          3. The SO42-/SO2 electrode potential is less than the Br2/Br- potential so sulfate ions cannot reduce the bromide ions.

          • 1, 2 and 3

          • Only 1 and 2

          • Only 2 and 3

          • Only 1

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