Q2 - Organic Experiments Flashcards

1
Q

Why is the first test tube of ethyne gas collected discarded?

A

It is less pure as it only contains displaced air

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2
Q

What is observed when dilute bromine solution is added to ethyne

A

Colour change from red to colourless

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3
Q

What is observed when dilute bromine solution is added to ethene

A

Colour change from red to colourless

→ unsaturated

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4
Q

What is observed when dilute acidified potassium manganate (VII) solution is added to ethyne

A

Colour change from purple to colourless

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5
Q

What is observed when dilute acidified potassium manganate (VII) solution is added to ethene

A

Colour change from purple to colourless
→ unsaturated

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6
Q

How would you test to see if ethyne gas is flammable

A

Hold a lighted taper at arms length above the mouth of the gas jar in a fume cupboard.
Burns with a luminous smoky flame

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7
Q

Describe the flame observed when ethyne gas is burned in air

A

Burns with a luminous smoky flame

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8
Q

How to prevent suck-back when preparing ethene

A

Remove delivery tube

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9
Q

How to prevent a fire when preparing ethene gas

A

Do not allow flame of Bunsen burner near the end of the delivery tube as the gas is flammable

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10
Q

What type of organic reaction occurs when bromine water is added to ethene gas

A

Addition reaction

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11
Q

Identify an organic product of the reaction between ethene and the bromine solution

A

2 - bromoethanol

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12
Q

Draw ethene apparatus

A
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13
Q

Draw ethyne apparatus

A
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14
Q

Describe the appearance of phenylmethanol at room temperature

A

Colourless liquid

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15
Q

Name a suitable piece of apparatus to measure accurately 1.5cm^3 of phenylmethanol

A

Graduated dropper

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16
Q

When preparing soap, why was the reaction mixture refluxed?

A

To bring the reaction to completion

17
Q

When preparing soap, suggest a suitable method for refluxing the reaction mixture and then distilling of the ethanol
Justify the suitability of your heating method

A

Hot water bath, ethanol distills off at 78°C

Mixture boils gently

18
Q

When preparing soap, why is it desirable to remove all the ethanol?

A

Makes it easier to isolate soap

19
Q

What colour change is observed when ethanal is oxidised to ethanoic acid using acidified potassium permanganate

A

Purple to colourless

20
Q

What colour change is observed when ethanal is oxidised to ethanoic acid using Fehling’s reagent

A

Royal blue to brick red

21
Q

What colour change is observed when ethanal is oxidised to ethanoic acid using the silver mirror test

A

A silver mirror is formed inside the test tube

22
Q

What colour change is observed when ethanal is oxidised to ethanoic acid using ammoniacal silver nitrate

A

A silver mirror is formed inside the test tube

23
Q

What can be concluded from the reactions of ethanal with acidified potassium permanganate, Fehling’s reagent and ammoniacal silver nitrate

*when compared to ketones, e.g. propanone

A

Aldehydes can be oxidised to carboxylic acids but ketones cannot

24
Q

What type of reaction is involved in the preparation of soap?

A

Saponification

Substitution

25
Q

What is the function of brine when preparing soap?

A

Precipitate soap

26
Q

Why is the ethanol i) added and ii) removed when preparing soap?

A

i) acts as a solvent

ii) to increase yield of soap

27
Q

When preparing benzoic acid, state and explain the colour change in the flask during the initial heating

A

Purple to brown

Mn +7 to Mn +4

28
Q

When preparing benzoic acid, name the organic compound that gave rise to the smell of almonds during the heating phase

A

Benzaldehyde

29
Q

When preparing benzoic acid, why was the solution acidified with concentrated hydrochloric acid

A
  • Convert sodium benzoate to benzoic acid
  • Neutralise any alkali (base) remaining in solution
  • Provide acidic medium to enable Mn +4 to be reduced to Mn +2
30
Q

When preparing benzoic acid, how do you test to ensure enough acid has been added?

A

Dip a rod in solution and touch it off moist blue litmus paper. The colour should go red

31
Q

When preparing benzoic acid, what was the purpose of adding the sodium sulphite solution ?

A

Reduces Mn +4 to Mn +2

32
Q

When preparing benzoic acid, why was the flask placed in ice before filtration

A

To ensure all benzoic acid crystallises out of solution

33
Q

Test for saturation example

A

Addition of bromine
If saturated - no colour change
If unsaturated - red to colourless

34
Q

Why is it preferable to use whole cloves instead of ground cloves?

A

Whole cloves contain more clove oil

35
Q

Describe the appearance of the product of steam distillation of clove oil and give the name of this type of mixture

A

Milky liquid

Emulsion

36
Q

Describe how you separated clove oil from cyclohexane

A
  • lower aqueous layer collected in beaker
  • drying agent (anhydrous MgSO4) added
  • solvent allowed to evaporate by placing beaker in water bath
37
Q

Draw eugenol

A
38
Q

What safety procedure must be carried out during liquid-liquid extraction?

A

Open tap of separating funnel

39
Q

Why is clove oil extracted by steam distillation?

A

Allows extraction at a temperature below its boiling point