OCR Gateway GCSE Chemistry

Topic Questions

2.1 Purity & Separating Mixtures

11 mark

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

  • Chromatography

  • Crystallisation

  • Distillation

  • Filtration

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21 mark

Which separation technique is this equipment used for?

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

  • Crystallisation

  • Distillation

  • Evaporation

  • Filtration

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31 mark

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

  • Chromatography

  • Distillation

  • Evaporation

  • Filtration

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41 mark

The molecular formula of cyclohexane is C6H12.

What is the empirical formula of cyclohexane?

  • CH

  • CH2

  • C6H12

  • C12H24

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11 mark

Which of the following is not a pure substance?

  • Seawater

  • Calcium carbonate

  • Distilled water 

  • Ammonia

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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

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3
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1 mark

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

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41 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

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51 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

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61 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

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71 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

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8
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1 mark

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

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91 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

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101 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 

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111 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

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121 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

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13
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1 mark

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

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14
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1 mark

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

  • 83.0

  • 90.0

  • 106.0

  • 130.0

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15
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1 mark

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

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161 mark

The molecular formula of decene is C10H20.

What is the empirical formula of decene?

  • CH2

  • C2H4

  • C5H10

  • C20H40

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171 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

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181 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

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191 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

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201 mark

Butane has the molecular formula C4H10.

What is the empirical formula of butane?

  • CH5

  • C2H5

  • C4H10

  • CH14

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211 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

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221 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

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231 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

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241 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

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251 mark

The molecular formula of hydrogen peroxide is H2O2.

What is the empirical formula of hydrogen peroxide?

  • H2O2

  • H2O

  • HO

  • H2O4

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261 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.

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