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Year 2 Chemistry OCR A level > Organic practical work > Flashcards

Organic practical work Flashcards

1
Q

Describe how the student would prepare the standard solution, naming apparatus and method (3 marks)

A
  • Dissolve solid in (distilled) water (less than 250 cm3) in beaker
  • Transfer (solution) to volumetric flask AND Transfer washings (from beaker) to flask
  • Make up to mark/up to 250 cm3 with (distilled) water AND Invert flask (several times to ensure mixing)
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2
Q

What does recrystallisation do

A

Purifies solids

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3
Q

What is the first step in recrystallisation

A

Dissolve solid in the minimum volume of hot solvent

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4
Q

After you’ve dissolved the solid in hot solvent when recrystallising, what is the next step

A

Allow the solution to cool down slowly, crystals will start to form

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5
Q

What is the name of the flask involved in reduced pressure filtration

A

Buchner

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6
Q

After allowing the solution to cool when recrystallising, what is the next step

A

Filter to remove the impurities in the solution and obtain the purified solid crystals

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7
Q

What is used to wash the purified crystals

A

Very cold solvent

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8
Q

Why must the solvent be cold when washing the crystals after recrystallisation

A

So solid product doesn’t dissolve again

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9
Q

What is the final step in recrystallisation

A

Leave crystals to dry

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10
Q

If a substance contains impurities, will the melting point be lower or higher than data book values

A

Lower

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11
Q

If the substance contains impurities, will the temperature range be smaller or larger than data book values

A

Larger range

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12
Q

What is the typical reaction of alkanes

A

Radical substitution

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13
Q

What is the typical reaction of alkenes

A

Electrophilic addition

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14
Q

What are the properties of alkenes

A
  • Electron rich double bond
  • Non-polar bond
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15
Q

What are the properties of aromatic compounds

A
  • Delocalised electron ring
  • Stable
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16
Q

What is the typical reaction of aromatic compounds

A

Electrophilic substitution

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17
Q

What are the 2 properties of alcohols

A
  • Lone pair on oxygen can act as a nucleophile
  • Polar C-OH bond
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18
Q

What are the 2 typical reactions with alcohols

A
  • Esterification and nucleophilic substitution
  • Dehydration/ elimination and nucleophilic substituion
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19
Q

What is the property of haloalkanes

A

Polar C-X bond

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20
Q

What is the typical reaction involving haloalkanes

A

Nucleophilic substitution and elimination

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21
Q

Properties of nitriles

A

Electron deficient carbon centre

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22
Q

Typical reaction of nitrile

A

Reduction and hydrolysis

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23
Q

Properties of amines

A

Lone pair on the nitrogen is basic, can act as a nucleophile

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24
Q

Typical reaction of amines

A

Nucleophilic substitution and neutralisation

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25
Q

Properties of aldehydes and ketones

A

Polar C=O bond

26
Q

Typical reactions of carbonyls (3 things)

A
  • Nucleophilic addition
  • Oxidation of aldehydes
  • Reduction
27
Q

Property of carboxylic acids

A

Electron deficient carbon centre

28
Q

Typical reactions of carboxylic acids

A
  • Esterification and neutralisation
29
Q

Properties of esters

A

Electron deficient carbon centre

30
Q

Typical reactions of esters

A

Hydrolysis

31
Q

Typical reaction of acid anhydride

A

Esterification

32
Q

Property of acid anhydride

A

Electron deficient carbon centre

33
Q

Typical reactions of acyl chloride

A
  • Nucleophilic addition-elimination
  • Condensation
  • Friedel-Crafts acylation
34
Q

Property of acyl chloride

A

Electron deficient carbon centre.

35
Q

What 3 functional groups are involved in addition reactions

A
  • Alkene
  • Aldehyde
  • Ketone
36
Q

What are the 3 functional groups involved in substitution reactions

A
  • Halogens
  • Benzene (H is substituted)
  • Alcohol
37
Q

What 2 functional groups are involved in elimination reactions

A
  • Halogens
  • Alcohols
38
Q

What 4 functional groups are involved in condensation reactions

A
  • Acyl chloride
  • Carboxylic acids
  • Amides
  • Alcohols
39
Q

What 2 functional groups are involved in hydrolysis reactions

A
  • Esters
  • Acid anhydride
40
Q

What are the 2/3 functional groups that can be oxidised

A
  • Primary alcohol
  • Aldehyde
  • Secondary alcohol
41
Q

What is reduction in terms of electrons

A

The gain of electrons

42
Q

Explain how TLC could be used to monitor the course of a reaction (2 marks)

A

Take samples from reaction mixture at regular intervals

Spot/run on a TLC plate, alongside cyclohexanol (and cyclohexanone) controls 9

43
Q

Plan an experiment to identify the pure organic ketone (3 marks)

A

React (sample of distillate) with 2,4-dinitrophenylhydrazine
recrystallise AND determine the melting point
Compare melting point to known/library value for
cyclohexanone (derivative)

44
Q

What are the steps to purify a liquid

A
  • Add a neutralising agent by formula or name e.g.
    Na2CO3
  • In separating funnel, organic layer is on top (as less dense as stated in original question
  • Drying with an anhydrous salt by formula or
    name, e.g. MgSO4, Na2SO4, CaCl2
  • Redistil
45
Q

Draw a distillation

A

distillation flask
heat source
thermometer at outlet (bulb level with outlet)
still-head
water condenser (correct direction of water
flow)
receiving vessel
open system.

46
Q

A reactant in solution reacts to form a solid. How can the solid be isolated (1 mark)

A

Filtration

47
Q

How can the solid be purified (1 mark)

A

Recrystallisation

48
Q

How could the purity of the solid be checked (1 mark)

A

TLC or melting point measurement

49
Q

How to separate a liquid product (1 mark)

A

Separating funnel

50
Q

Organic liquid may still have some water present. How can this be removed before purification (1 mark)

A

By adding a (solid) drying agent (such as Na2SO4/MgSO4/CaO)

Filtering off the unwanted solid

51
Q

How can the liquid be purified (1 mark)

A

Distillation

52
Q

How could the purity of the dry liquid be checked, after purification (1 mark)

A

Chromatography

53
Q

A reaction in aqueous solution forms a slat that is soluble in water. The aim is to isolate the acid of the salt and then purify it. The acid is a liquid that is not soluble in water. How can the acid be formed and then isolated (1 mark)

A

Add acid then separating funnel

54
Q

How can the acid be purified (1 mark)

A

Distillation

55
Q

How can the purity of the liquid be checked (1 mark)

A

Chromatography

56
Q

List the equipment used in a reflux (3 marks)

A

Round-bottomed or pear-shaped flask (1)

Condenser (1)

Anti-bumping granules (1

57
Q

How could we carry out a quick test to distinguish an aldehyde from a ketone (2 marks)

A

Tollens: warm with Tollens reagent (or AgNO3/NH3) (1)

Silver mirror (1)

58
Q

How could we carry out a quick test to distinguish an alcohol from a ketone (2 marks)

A

Cr2O72-/H+ (1)

Orange to green (1)

Allow DNPH/organe ppte for (2)

59
Q

How could we carry out a quick test for a haloalkane that also identifies the halide (3 marks)

A

AgNO3 (HNO3) (1)

NaOH (1)

White, cream or yellow precipitate (1)

(redissolves in conc. NH3 if AgBr and in dil. NH3 if AgCl)

60
Q

How could we carry out a quick test for a carboxylic acid (2 marks)

A

Na2CO3 (1)

Effervescence (1)

61
Q

How could we carry out a quick test for phenol but not benzene (3 marks)

A

Br2 (aq) (1)

Decolourised bromine (1)

White precipitate (1)

62
Q

Esterifcation happens when an alcohol and a carboxylic acid are reacted together. The product ester will often have a boiling point above room temperature and is also often immiscible with water. Esters are typically less dense than water. Carboxylic acids and alcohols will dissolve in water, as will the catalytic acid. Write down the steps required to purify an ester, and to ensure that no alcohol, carboxylic acid or catalytic acid remain in the product (6 marks)

A

Separating funnel (1)

Collect non-aqueous TOP layer (1) (mark for stating product is the top layer)

Wash in funnel with aq. Na2CO3/NaHCO3 (open tap to allow gas to escape) (1)

Dry organic layer with drying agent (1)

Filter (1)

Distil (1)

Year 2 Chemistry OCR A level (20 decks)

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