GCSEScienceOCRCombined Science A (Gateway)ChemistryExam QuestionsElements, compounds & mixturesPurity & Separating Mixtures

Purity & Separating Mixtures (OCR GCSE Combined Science A (Gateway): Chemistry): Exam Questions

Exam code: J250

2 hours43 questions

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Purity & Separating Mixtures

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11 mark

Which technique is the best for separating pure water from a solution of sodium chloride in water?

  • Chromatography

  • Crystallisation

  • Distillation

  • Filtration

Choose your answer

21 mark

Which separation technique is this equipment used for?

q1-paper-1-nov-2020-ocr-gcse-chem

  • Crystallisation

  • Distillation

  • Evaporation

  • Filtration

Choose your answer

31 mark

Which purification technique is used to separate ethanol and water from a mixture?

  • Chromatography

  • Distillation

  • Evaporation

  • Filtration

Choose your answer

41 mark

The molecular formula of cyclohexane is C6H12.

What is the empirical formula of cyclohexane?

  • CH

  • CH2

  • C6H12

  • C12H24

Choose your answer

5
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A company produces tin from an ore called cassiterite, which is mainly tin oxide.

What is the relative formula mass (Mr) of tin oxide, SnO2?

Relative atomic masses (Ar):   Sn= 119 O= 16

  • 135

  • 151

  • 270

  • 1904

Choose your answer

61 mark

Which equipment is needed for distillation?

  • Condenser, funnel, thermometer

  • Condenser, round-bottomed flask, thermometer

  • Thermometer, beaker, pH probe

  • Thermometer, measuring cylinder, filter paper

Choose your answer

71 mark

A student investigates some samples using gas chromatography.

The student also measures the melting point of each sample.

Which results should the student expect from a pure sample?

 

Gas chromatogram

Melting point (°C)

A

3 peaks

123–127

B

1 peak

123–127

C

2 peaks

125

D

1 peak

125

    Choose your answer

    81 mark

    What is the relative formula mass of iron chloride, FeCl3?

    Relative atomic mass (Ar): Cl = 35.5       Fe = 55.8

    • 91.3

    • 126.8

    • 162.3

    • 202.9

    Choose your answer

    11 mark

    Which of the following is not a pure substance?

    • Seawater

    • Calcium carbonate

    • Distilled water 

    • Ammonia

    Choose your answer

    21 mark

    A student was investigating the colours in black food colouring. 

    Chromatography was carried out on samples A-E and compared to the black food colouring. 

    The following chromatogram was produced. 

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    Which of the following conclusions is not true for this chromatogram?

    • Sample B is insoluble in the solvent used 

    • Samples C and D are pure substances 

    • Sample D is the least soluble of the samples

    • The black ink is a mixture of  A, E and an unknown

    Choose your answer

    31 mark

    A student set up the following apparatus to investigate the colours in three different food colourings.  

    q5-ocr-gcse-mcq

    What are the stationary and mobile phases for this experiment? 

     

    Stationary 

    Mobile

    A

    chromatography paper 

    water

    B

    beaker

    start line

    C

    water

    food colourings

    D

    start line

    chromatography paper

      Choose your answer

      41 mark

      A student making copper sulfate crystals used the method below. 

      q6-ocr-gcse-mcq

      Unreacted copper carbonate was left over as it had been added in excess.

      Which separation technique could be used to separate the unreacted copper carbonate and solution into different containers?

      • Filtration

      • Crystallisation

      • Simple distillation

      • Fractional distillation

      Choose your answer

      51 mark

      A mixture contains methanol and ethanol. They have different boiling points. 

      Which method could be used to separate this mixture?

      • Filtration

      • Simple distillation

      • Crystallisation

      • Evaporation

      Choose your answer

      6
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      A student carried out chromatography on a sample of green ink. 

      q8-ocr-gcse-mcq

      The distance moved by the solvent front is 5.8 cm. 

      The distance moved by the yellow dye is 4.5 cm.

      Calculate the Rf value of the yellow dye to 2 significant figures. 

      • 0.78

      • 0.80

      • 1.3

      • 26

      Choose your answer

      71 mark

      The diagram below shows a heating curve for a pure substance.

      q9-ocr-gcse-mcq

      Which part of the curve shows a change of state happening?

      • A to B

      • B to C

      • C to D 

      • B to D

      Choose your answer

      81 mark

      A student separates the colours in a sample of black ink using paper chromatography.

      • He puts a spot of black ink onto a piece of filter paper.

      • He dips the filter paper into ethanol in a beaker.

      What phase describes ethanol in this experiment?

      • Gas phase

      • Mobile phase

      • Solid phase

      • Stationary phase

      Choose your answer

      9
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      Look at the chromatogram.

      q2-paper-3-specimen-2016-ocr-gcse-chem

      What is the Rf value of the green spot? Use a ruler to help you.

      • 0.17

      • 0.42

      • 0.83

      • 1.00

      Choose your answer

      10
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      What is the relative formula mass of sodium carbonate, Na2CO3?

      • 83.0

      • 90.0

      • 106.0

      • 130.0

      Choose your answer

      11
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      The formula of magnesium chloride is MgCl2.

      What is the relative formula mass of magnesium chloride?

      (Ar: Mg = 24.3, Cl = 35.5)

      • 59.8

      • 95.3

      • 119.6

      • 84.1

      Choose your answer

      121 mark

      The molecular formula of decene is C10H20.

      What is the empirical formula of decene?

      • CH2

      • C2H4

      • C5H10

      • C20H40

      Choose your answer

      131 mark

      Rf values are used to compare the different spots on a chromatogram.

      What is the formula used to calculate an Rf value?

      • straight R subscript straight f space equals space fraction numerator distance space travelled space by space solvent over denominator distance space travelled space by space substance end fraction

      • straight R subscript straight f space equals space fraction numerator distance space travelled space by space substance over denominator distance space travelled space by space solvent end fraction

      • straight R subscript straight f space equals space fraction numerator distance space travelled space by space stationary space phase over denominator distance space travelled space by space mobile space phase end fraction

      • straight R subscript straight f space equals space fraction numerator distance space travelled space by space solvent over denominator distance space travelled space by space mobile space phase end fraction

      Choose your answer

      141 mark

      The formula of sulfuric acid is H2SO4.

      What is the relative formula mass, Mr, of sulfuric acid?

      The relative atomic mass, Ar, of H is 1, of S is 32 and of O is 16.

      • 49

      • 98

      • 130

      • 200

      Choose your answer

      151 mark

      In some remote islands, drinking water is made from sea water.

      What is the name of the process for making drinking water from sea water?

      • Chlorination

      • Distillation

      • Filtration

      • Sedimentation

      Choose your answer

      161 mark

      Butane has the molecular formula C4H10.

      What is the empirical formula of butane?

      • CH5

      • C2H5

      • C4H10

      • CH14

      Choose your answer

      171 mark

      Which statement correctly describes a pure substance?

      • Consists of just one element or compound

      • Has a low melting point

      • Is a mixture of two or more substances

      • Melts over a range of temperatures

      Choose your answer

      181 mark

      A student separates the colours of black ink using paper chromatography.

      • He puts a spot of black ink onto a piece of filter paper.

      • He dips the filter paper into ethanol in a beaker.

      What phase describes ethanol in this experiment?

      • Gas phase

      • Mobile phase

      • Solid phase

      • Stationary phase

      Choose your answer

      191 mark

      Paper chromatography can be used to separate the colours in ink.

      Water is the solvent used to separate the colours in water soluble ink.

      What name is given to the water used in paper chromatography?

      • Absorption phase

      • Liquid phase

      • Mobile phase

      • Stationary phase

      Choose your answer

      201 mark

      The molecular formula of hydrogen peroxide is H2O2.

      What is the empirical formula of hydrogen peroxide?

      • H2O2

      • H2O

      • HO

      • H2O4

      Choose your answer

      211 mark

      A gas chromatogram is a chart that represents different substances in a mixture.

      q14-paper-4-june-2018-ocr-gcse-chem

      Which of the following statements about a gas chromatogram is not correct?

      • A gas chromatogram can detect very small amounts of substances.

      • One compound produces several peaks

      • The area of each peak shows the relative amount of each substance.

      • The retention time is different for different substances.

      Choose your answer

      11 mark

      The gas chromatogram shows the different substances in a gas mixture. 

      q10-ocr-gcse-mcq

      Which statement below is not true? 

      • The mixture contains six substances 

      • Substance A has the shortest retention time 

      • The relative amounts of substance D and E are very similar

      • Substance F has the greatest affinity for the mobile phase 

      Choose your answer

      21 mark

      The formula of ammonium carbonate is (NH4)2CO3.

      What is the relative formula mass of ammonium carbonate?

      (Ar: C = 12, H = 1, N = 14, O = 16)

      • 78

      • 90

      • 96

      • 120

      Choose your answer

      31 mark

      A student separates a dye using thin layer chromatography.

      She puts a thin layer of solid alumina onto a glass plate. She puts the dye on the pencil line. She puts the glass plate into a tank containing water.

      Which of the following is the stationary phase?

      • Alumina

      • Glass

      • Pencil line

      • Water

      Choose your answer

      4
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      The empirical formula of a compound is CH2O.

      The relative formula mass of the compound is 180.0.

      What is the molecular formula of the compound?

      Relative atomic mass (Ar): C = 12.0 H = 1.0 O = 16.0

      • C4H8O4

      • C5H10O5

      • C6H12O6

      • C7H14O7

      Choose your answer

      51 mark

      The diagram shows the displayed formula of succinic acid. 

      q4-ocr-gcse-mcq

      What is the empirical formula for this compound?

      • C4H6O4

      • CH2O

      • C2H3O2

      • CHO

      Choose your answer