ASChemistryOCRExam Questions4. Core Organic ChemistryHaloalkanes

Haloalkanes (OCR AS Chemistry A): Exam Questions

Exam code: H032

3 hours38 questions

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Haloalkanes

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1
1 mark

Which reaction is an example of nucleophilic substitution?

  • CH3CH2Br → CH2=CH2 + HBr

  • CH2=CH2 + HBr → CH3CH2Br

  • C3H7Br + NH3 → C3H7NH2 + HBr

  • C2H6 + Br2 → C2H5Br + HBr

Choose your answer

2
1 mark

What is the correct systematic name and classification of the following molecule?

Displayed structure CH3CH2CH2CHBrCH3

Systematic name

Classification

A

1-bromopentane

Primary

B

2-bromopentane

Secondary

C

2-bromopentane

Primary

D

4-bromopentane

Secondary

    Choose your answer

    3
    1 mark

    Which of the following statements is not correct about the depletion of the ozone layer?

    • CFCs produce free radicals when they are exposed to UV light in the upper atmosphere

    • 2 moles of ozone break down to form 3 moles of oxygen

    • Fluorine and chlorine free radicals can break down ozone molecules in the upper atmosphere

    • The mechanism is a radical-catalysed decomposition reaction

    Choose your answer

    4
    1 mark

    Three haloalkanes are heated separately with aqueous silver nitrate in ethanol. Each reaction produces a precipitate.

    Which haloalkane produces a precipitate the fastest?

    • 1-iodopropane

    • They precipitate at the same rate

    • 1-chloropropane

    • 1-bromopropane

    Choose your answer

    5
    1 mark

    Which statement about a nucleophile is correct?

    • It is an electron pair donor

    • It is an electron pair acceptor

    • It is a proton acceptor

    • It is a proton donor

    Choose your answer

    6
    1 mark

    Which compound has the fastest rate of reaction with aqueous potassium hydroxide to form an alcohol?

    • 1- chlorobutane

    • 1-bromobutane

    • 1-fluorobutane

    • 1-iodobutane

    Choose your answer

    7
    1 mark

    Which statement about ozone is not correct?

    • It decomposes to form oxygen

    • Ozone holes are regions of the upper atmosphere where there is a reduced concentration of ozone

    • Hydrofluorocarbons are more damaging to the ozone layer than chlorofluorocarbons

    • It absorbs ultraviolet radiation from the Sun

    Choose your answer

    8
    1 mark

    The equation for the alkaline hydrolysis of 1-iodopropane is shown below 

    CH3CH2CH2I + OH– →CH3CH2CH2OH + I –

    What is the name of the mechanism used for this reaction? 

    • Electrophilic addition

    • Elimination

    • Nucleophilic substitution

    • Oxidation

    Choose your answer

    9
    1 mark

    Which row shows the correct shape and bond angle in a molecule of CF2Cl2?

    Shape

    Bond angle

    A

    Linear

    180°

    B

    Pyramidal

    107°

    C

    Tetrahedral

    109.5°

    D

    Trigonal planar

    120°

      Choose your answer

      10
      1 mark

      Which statement explains why haloalkanes are more reactive than alkanes?

      • Carbon is more electronegative than the halogens

      • The carbon and halogen atoms have different electronegativities

      • Carbon-halogen bonds are stronger than carbon-hydrogen bonds

      • The carbon-halogen bond is non-polar

      Choose your answer

      1
      1 mark

      A chemist adds four drops of 1-chloropentane, 1-bromopentane and 1-iodopentane separately to three test-tubes containing 1.0 cm3 of aqueous silver nitrate at 60 °C. A hydrolysis reaction occurred.

      Which statement best explains why 1-iodopentane precipitates first and 1-chloropentane precipitates last?

      • The bond polarity decreases from C-Cl to C-I

      • The electronegativity of the halogens decreases down the group

      • The bond enthalpy decreases from C-Cl to C-I

      • The ionisation energy of the halogens decreases from Cl to I

      Choose your answer

      2
      1 mark

      Which statement best describes the mechanism of the reaction between aqueous sodium hydroxide and 2-bromopropane?

      • Attack by a nucleophile on a carbocation

      • Attack by a nucleophile on a carbon atom with a partial positive charge

      • Homolytic bond fission and attack by a nucleophile on a carbocation

      • Homolytic bond fission and attack by an electrophile on a partial positive charge

      Choose your answer

      3
      1 mark

      In the hydrolysis of bromoethane by aqueous sodium hydroxide, what is the nature of the attacking species and of the leaving group?

      Attacking group

      Leaving group

      A

      nucleophile

      nucleophile

      B

      electrophile

      nucleophile

      C

      nucleophile

      electrophile

      D

      electrophile

      electrophile

        Choose your answer

        4
        1 mark

        Which reagents and conditions are required for the following reaction?

        CH3CH2CH2I → CH3CH2CH2OH

        • Heated under reflux, aqueous potassium cyanide

        • Heated under reflux, ethanol, potassium cyanide

        • Heated under reflux with aqueous sodium hydroxide 

        • Warm with a solution of ethanol 

        Choose your answer

        5
        1 mark

        Which pair of reactions shows the correct sequence of attack of CFC molecules with ozone?

         

        Reaction 1

        Reaction 2

        A

        F● + O3 → FO● + O2

        FO● + O3 → 2O2 + F●

        B

        Cl + O3 → ClO● + O2

        ClO● + O3 → 2O2 + Cl

        C

        Cl● + O3 → ClO● + O2

        ClO● + O3 → 2O2 + Cl●

        D

        Cl● + O3 → ClO + O2

        ClO + O3 → 2O2 + Cl●

          Choose your answer

          6
          1 mark

          What is the correct systematic name and classification of the following molecule?

          Chemical structure, CH3CH3C(CH3)BrCH3

          Systematic name

          Classification

          A

          2-methyl-2-bromobutane

          Tertiary

          B

          3-methyl-3-bromobutane

          Secondary

          C

          2-bromo-2-methylbutane

          Secondary

          D

          2-bromo-2-methylbutane

          Tertiary

            Choose your answer

            7
            1 mark

            The presence of a halogen in an organic compound may be detected by warming the organic compound with aqueous silver nitrate in ethanol.

            Which compound would be the quickest to produce a precipitate?

            • 1,2,3-trichlorobutane 

            • 1,2-dichloro-3-fluorobutane 

            • 1,2-difluoro-3-iodobutane 

            • 1-bromo-2-chloro-3-fluorobutane 

            Choose your answer

            8
            1 mark

            The breakdown of the ozone layer can be catalysed by NO● radicals.

            Which equation is a propagation step in the mechanism for this process?

            • NO2● + O → NO● + O

            • NO● + O3 → NO2● + O2

            • O3 + O → 2O2

            • NO● + O2 → NO2● + O3

            Choose your answer

            9
            1 mark

            Dichlorodifluoromethane, CCl2F2, has been used in aerosol propellants and as a refrigerant.

            Which statement helps to explain why dichlorodifluoromethane is chemically inert?

            • The carbon-fluorine bond energy is large

            • The carbon-fluorine bond has a low polarity

            • Fluorine is highly electronegative

            • Fluorine compounds are non-flammable

            Choose your answer

            10
            1 mark

            Which compound does not react with nucleophiles?

            • CH3CH2CH2OH

            • CH2CH2CHO

            • CH3CH2CH2Cl

            • CH3CH2CH2CH3

            Choose your answer

            11
            1 mark

            Hydrogen bromide reacts with 3-methylbut-1-ene.

            What is the structure of the major intermediate formed in the mechanism?

            • c88ab9b5-3d9e-4248-8793-102c5c472c9b


            • 2dc09a2b-7e22-4ffd-88a0-608f15c45fb4
            • 34e52511-4260-43a0-bbb6-1f7ad95cb744
            • ef8e1e8a-a493-4e5a-aaf2-1cda98504930

            Choose your answer

            1
            1 mark

            Which statements is/are correct about haloalkanes?

            1. Published bond enthalpies may differ because they are calculated as a mean average across different chemical environments, not just within one compound.

            2. Haloalkanes that contain a C-F bond are the least reactive because this bond has the highest bond enthalpy.

            3. When heated with aqueous silver nitrate in ethanol, the haloalkane that takes the longest to form a precipitate is a chloroalkane.

            • 1, 2 and 3

            • Only 1 and 2

            • Only 2 and 3

            • Only 1

            Choose your answer

            2
            1 mark

            Which statements is/are correct?

            1. The OH- ion is a better nucleophile than water.

            2. During nucleophilic substitution, the carbon-halogen bond breaks homolytically forming a halide ion.

            3. Nucleophiles are 'nucleus loving' so are themselves positively charged.

            • 1, 2 and 3

            • Only 1 and 2

            • Only 2 and 3

            • Only 1

            Choose your answer

            3
            1 mark

            Which statement about haloalkanes is correct?

            • Haloalkanes and alcohols both take part in dehydration reactions to produce alkenes

            • Haloalkanes are soluble in water due to the polar carbon-halogen bond

            • The OH- ion acts as a base in an elimination reaction

            • Hot ethanolic NaOH is used to produce the nucleophile in a substitution reaction

            Choose your answer

            4
            1 mark

            Which statements is/are not correct about the depletion of the ozone layer?

            1. CH3F will produce a fluorine radical and a CH3 radical in the presence of UV radiation.

            2. CH2ClF is a common example of a hydrofluorocarbon used in refrigerators.

            3. Chlorofluorocarbons are preferred to hydrofluorocarbons because they cause less depletion of the ozone layer.

            • 1, 2 and 3

            • Only 1 and 2

            • Only 2 and 3

            • Only 1

            Choose your answer

            5
            1 mark

            The breakdown of ozone is catalysed by NO radicals.

            Which equation shows a propagation step in the mechanism for this process?

            • NO● + ●NO2 → N2O + O2

            • NO2● + O → NO● + O2

            • N2 + O2 → NO● + NO●

            • NO● + O3 → NO2 + ●O2

            Choose your answer