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A LevelChemistryOCRExam Questions4. Core Organic Chemistry4.7 Analytical Techniques

Analytical Techniques (OCR A Level Chemistry)

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4.7 Analytical Techniques

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4.7 Analytical Techniques

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11 mark

Which alcohol is not likely to have a fragment ion at m/z = 43 in its mass spectrum?

  • CH3CH2CH(OH)CH3

  • CH3CH2CH2CH2OH

  • CH3CH(OH)CH2CH2CH3

  • (CH3)2CHCH2OH

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21 mark

Which organic functional group could have produced the infrared spectrum below?

ir-spectrum-ocr

  • An aldehyde

  • An alcohol

  • A carboxylic acid

  • A ketone

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31 mark

Which group of compounds could not be differentiated from each other using ONLY infrared spectroscopy?

  • Propane, propan-1-ol, propan-2-one, propanoic acid.

  • Propane, propanoic acid, propan-1-ol, propanal

  • Propane, propan-2-ol, propan-2-one, propanoic acid

  • Propanoic acid, propanal, propan-2-one, propane

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4
Sme Calculator1 mark

Which compound could show a small M+1 peak at m/z = 73?

  • Pent-1,3-diene 

  • Pentane 

  • Cyclopentane 

  • Butan-2-ol 

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11 mark

Which compound could have produced the infrared spectrum below?

ocr-4-7m-q1

  • Butanal

  • Butanoic acid

  • Butan-1-ol

  • But-1-ene

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21 mark

An unknown organic compound produced the infrared spectrum below.

ocr-4-7m-q2

Which conclusion(s) is / are correct about the unknown organic compound?

  1. It is an aldehdye
  2. It is a ketone
  3. It is a carboxylic acid

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

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31 mark

Butanal, CH3CH2CH2CHO, and butanone, CH3CH2COCH3, are carbonyl compounds. 

When these compounds are compared using analytical methods, which of the following statements is not correct?

  • The compounds produce different patterns in the fingerprint region of the IR spectrum

  • The carbonyl groups absorb at frequencies in the same region of the IR spectrum

  • The compounds have molecular ion peaks at different mass to charge ratios in a mass spectrum

  • The compounds produce different fragmentation patterns in a mass spectrum

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41 mark

Which statement(s) is / are possible uses and applications of infrared spectroscopy?

  1. Carbon dating
  2. Monitoring localised pollution
  3. Roadside breathalysers

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

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51 mark

Which alcohol is not likely to have a fragment ion at m/z = 29 in its mass spectrum

  • CH3CH2CH2OH

  • CH3CH(OH)CH2CH3

  • (CH3)2CH(OH)

  • CH3CH2CH(OH)CH2CH3 

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61 mark

Bromine exists as two isotopes 79Br and 81Br, which are found in almost equal abundance.

Which of the following statements is correct?

  • 79Br is more reactive than 81Br

  • The mass spectrum of C3H7Br has two molecular ion peaks at 122 and 124

  • The atomic radius of 79Br is less than the atomic radius of 81Br

  • The first ionisation energy of 79Br is less than the first ionisation energy of 81Br

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71 mark

Which ketone is likely to have fragment ions at m/z = 15 and m/z = 43 but not at m/z = 29 in its mass spectrum?

  • Pentan-3-one

  • 3-methylbutanone

  • Hexan-3-one

  • Butanone

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8
Sme Calculator1 mark

A compound has the composition by mass:

   C, 52.2%; H, 13.0%; O, 34.8%

Which compound has this composition?

  • CH3CHO

  • CH3COOH

  • HCOOCH3

  • C2H5OH

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91 mark

Which pair of compounds would you expect to both have a singly charged peak at m/z = 29 in the mass spectrum?

  • Propanal and propanone

  • Propan-1-ol and propanal

  • Propan-2-ol and propanal

  • Propanone and propan-2-ol

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101 mark

Which compound could produce the IR spectrum below? 

ocr-as-4-7-q10-ch3chohcn-ir-spec

  • CH3COOH

  • CH3CONH2 

  • CH3CH2OH

  • CH3CHOHCN

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11 mark

An alcohol A is heated under reflux with sulfuric acid and potassium dichromate(VI).
The organic compound formed produces the infrared spectrum below.

ir-spectrum

Which compound could be alcohol A?

  • option-a-

     

  • A3rLRpd9_option-b

     

  • option-c 
      

  • option-d

     

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21 mark

Analysis of an unknown organic compound yields the following information.

  • A narrow peak at 3200 - 3600 cm-1 on an infrared spectrum.
  • 43.24% by mass of oxygen and 8.11% by mass of hydrogen.
  • A colourless solution when tested with Tollens’ reagent.

What is the identity of the unknown organic compound?

  • 3-hydroxypropanoic acid

  • 3-hydroxypropanal

  • 1-hydroxypropanone

  • 2-oxopropanoic acid

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31 mark

Which of the following statements is/are correct?

  1. Chemical bonds will absorb infrared energy that has an amplitude equal to its natural vibration and therefore increase the resonance.
  2. Infrared energy is only absorbed if the molecule has a permanent dipole.
  3. Resonance frequency is the reciprocal of the wavelength.

  • 1, 2 and 3

  • Only 1 and 2

  • Only 2 and 3

  • Only 1

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41 mark

Which statement about propanal, prop-2-en-1-ol and butane is not correct?

  • Mass spectroscopy can be used to distinguish between propanal and prop-2-en-1-ol. 

  • One molecule will show a peak at m / z = 43 on a mass spectrum. 

  • The fingerprint region on an infrared spectrum alone is enough to identify a molecule.

  • The order of increasing boiling points is butane, propanal, prop-2-en-1-ol.

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51 mark

Multiple analytical techniques were carried out on molecule X with the following results.

  • Molecule X has an empirical formula of C2H4O
  • The infrared red spectrum showed a narrow peak at 3400 cm-1 and a second peak at 1720 cm-1.
  • The mass spectrum showed fragment ion peaks at m / z = 15, 43, 45 and 73.

  • Butanoic acid

  • 2-hydroxybutanal

  • 4-hydroxybutanal

  • 3-hydroxybutan-2-one

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