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Aqa Chemistry Test Tube Reactions > Testing For Organic Functional Groups > Flashcards

Testing For Organic Functional Groups Flashcards

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1
Q

Test for alkenes

A

Add bromine water

Solution goes from orange -> colourless

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2
Q

Test for an aldehyde

A

Test with tollens reagent a silver mirror should form

Test with fehlings reagent
Solution goes from blue -> red precipitate

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3
Q

Test for carboxylic acid

A

Add sodium carbonate

Effervescence of carbon dioxide should evolve

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4
Q

Test for primary alcohols

A

Warm solution with acidified potassium dichromate
Colour change from Orange -> green

Under distillation primary alcohols oxidise to aldehydes then carboxylic acids

Test for carboxylic acid: add sodium carbonate
If effervescence of co2 then it’s a primary alcohol

Test for aldehyde: Add Tollens reagent
If silver mirror is formed then it’s a primary alcohol
Add fehlings solution
If colour change from blue -> red precipitate then it’s a primary alcohol

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5
Q

Test for secondary alcohols

A

Warm solution with acidified potassium dichromate
Colour change from Orange -> green

When secondary alcohols are oxidised under reflux a ketone is produced

Test with Fehlings and Tollens a negative results indicates the presence of the ketone and therefore it’s a secondary alcohol

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6
Q

Test for a chloroalkane

A

Warm with silver nitrate solution (AgNO3)

AgCl (s) -> white precipitate
AgBr (s) -> cream precipitate
AgI (s) -> yellow precipitate

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7
Q

Test for group 2 metal cations

A

Add dilute sodium hydroxide

MgCl2 + 2NaOH → Mg(OH)2 + 2NaCl
White precipitate formed

CaBr2 + 2NaOH → Ca(OH)2 + 2NaBr
White precipitate formed

SrCl2 + 2NaOH → Sr(OH)2 + 2NaCl
White precipitate

BaCl2 + 2NaOH → Ba(OH)2 + 2NaCl
Colourless solution formed

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8
Q

Test for group 2 metal cations

A

Add dilute sulphuric acid

MgCl2 + H2SO4 → MgSO4 + 2HCl
Colourless solution

CaBr2 + H2SO4 → CaSO4 + 2HBr
White precipitate

SrCl2 + H2SO4 → SrSO4 + 2HCl
White precipitate

BaCl2 + H2SO4 → BaSO4 + 2HCl
White precipitate formed

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9
Q

Test for ammonium ions

A

Warm with sodium hydroxide in a fume cupboard

NH4Cl + NaOH → NH3 + NaCl + H2O

Test ammonia gas produced with damp litmus paper the paper should turn blue

Litmus detects alkaline or acidic , Ammonia gas is alkaline therefore it turns blue

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10
Q

Test for carbonate ions in aqueous solution

A

Add calcium hydroxide (limewater) to sodium carbonate

Limewater solution goes from
colourless -> cloudy

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11
Q

Test for sulphate ions

A

Add dilute HCl and the barium chloride solution

Solution will turn cloudy and a white precipitate is formed

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12
Q

Test for halide ions in aqueous solution

A

Add dilute nitric acid followed by silver nitrate

Potassium chloride- white precipitate
Potassium bromide- cream precipitate
Potassium iodide- yellow precipitate

To distinguish between similar colours add ammonia solution

Potassium chloride- dissolves forming colourless solution

Potassium bromide- only dissolves in concentrated ammonia solution

Potassium iodide- doesn’t dissolve at all reminds a yellow precipitate

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13
Q

Testing halide ions using concentrated. H2SO4

A

Potassium chloride- solution remains white produces effervescence

Potassium bromide- solution turns dark brown
Brown gas /effervescence

Potassium iodide - solution turns bright orange
Effervescence

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14
Q

Period II oxides

A

Reaction in air Flame

Na2O vigorous Yellow
MgO. vigorous Brilliant white
Al2O3. Slow N/A
SiO2. Slow N/A
P4O10 Spontaneous Brilliant white
Combustion
SO2. Burns steadily. Blue

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15
Q

In aqueous solution

Fe(H2O)6 2+

A

Green solution

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16
Q

In aqueous solution

Cu(H2O)6 2+

A

Blue solution

17
Q

In aqueous solution

Fe(H2O)6 3+

A

Pale violet but appears orange due to hydrolysis to Fe(H2O)5(OH) 2+

18
Q

In aqueous solution

Al(H2O)6 3+

A

Colourless solution

19
Q

Reaction of Fe(H2O)6 2+ with sodium hydroxide

A

Fe(H2O)4(OH)2
Green precipitate

Darkens on standing as its oxidised to Fe(H2O)3(OH)3

In excess= no further reaction

20
Q

Reaction of Cu(H2O)6 2+ with sodium hydroxide

A

Cu(H2O)4(OH)2

Blue precipitate formed

In excess= no further reaction

21
Q

Reaction of Fe(H2O)6 3+ with sodium hydroxide

A

Fe(H2O)3(OH)3

Brown precipitate formed

In excess = no further reaction

22
Q

Reaction of Al(H2O)6 3+ with sodium hydroxide

A

Al(H2O)3(OH)3

White precipitate formed

In excess = Al(H2O)2(OH)4 1-
Redissolves to give a colourless solution

23
Q

Reaction of Metal Aqua ions with NH3

A

Same as the relations with sodium hydroxide

Except in excess Cu(H2O)4(OH)2 forms Cu(H2O)2(NH3)4 2+
Which is a dark blue solution

24
Q

Reaction of Fe(H2O)6 2+ with CaCO3

A

FeCO3

Green precipitate

25
Q

Reaction of Cu(H2O)6 2+ with CaCO3

A

CuCO3

Blue-green precipitate

26
Q

Reaction of Fe(H2O)6 3+ with CaCO3

A

Fe(H2O)3(OH)3

Brown precipitate and bubbles of gas (CO2)

27
Q

Reaction of Al(H2O)6 3+ with CaCO3

A

Al(H2O)3(OH)3

White precipitate and bubbles of gas (CO2)

28
Q

Substitution reaction of Fe(H2O)6 2+ with HCl

A

FeCl4 2-

Yellow solution

29
Q

Substitution reaction of Cu(H2O)6 2+ with HCl

A

CuCl4 2-

Green solution

30
Q

Substitution reaction of Fe(H2O)6 3+ with HCl

A

FeCl4 1-

Yellow solution

31
Q

Substitution reaction of Al(H2O)6 3+ with HCl 11

A

AlCl4 1-

Colourless solution

32
Q

Distinguishing between halogens

A

Add an aqueous solution of chlorine
Displaces elements that are Lower

Halogen In water With cyclohexane

Cl2 Green. Green

Br2. Orange. Orange

I2. Brown. Violet

Cl2 + 2Br- → Br2 + 2Cl-

Cl2 + 2I- → I2 + 2Cl-

33
Q

NaF and NaCl with sulfuric acid

A

NaCl (s) +H2SO4 (l) → NaHSO4 (s) +HCl (g)
Produces steamy HCl fumes

NaF (s) +H2SO4 (l) → NaHSO4 (s) +HF (g)
produces steamy HF fumes

HF & HCl aren’t strong enough reducing agents to reduce sulfuric acid so reaction stops

Not a redox reaction, oxidation states remain the same

34
Q

NaBr with sulfuric acid

A

NaBr (s) +H2SO4 (l) → NaHSO4 (s) +HBr (g)
Produces steamy HBr fumes

HBr strong enough to reduce sulfuric acid so it reacts further

2HBr(aq) + H2SO4 (l) → Br2 (g) + SO2 (g) + 2H2O (l)

Choking fumes of SO2
Orange fumes Br2

35
Q

NaI with sulfuric acid

A

NaI (s) +H2SO4 (l) → NaHSO4 (s) +HI (g)
Produces steamy HI fumes

HI strong enough to reduce sulfuric acid so it reacts further

2HI(aq) + H2SO4 (l) → I2 (g) + SO2 (g) + 2H2O (l)

HI strongest reducing agent so further reduces SO2

6HI(g) + SO2 (g) → H2S (g) + 3I2 (s) + 2H2O (l)

H2S toxic eggy smell
I2 purple gas/ grey solid

36
Q

Halogen properties

A

Colour. State

F2. Pale yellow. Gas
Cl2. Green. Gas
Br2 Red-brown Liquid
I2. Grey Solid

37
Q

Displacement Reaction with chlorine water

A

Potassium chloride - no reaction

Potassium bromide - colourless -> orange solution of Br2 formed

Potassium iodide - colourless -> brown solution I2 formed

38
Q

Displacement reaction with bromine water

A

Potassium chloride - no reaction

Potassium bromide - no reaction

Potassium iodide - colourless -> brown solution of I2

39
Q

Displacement reaction with iodine solution

A

Potassium chloride - no reaction

Potassium bromide - no reaction

Potassium iodide - no reaction

Aqa Chemistry Test Tube Reactions (1 decks)

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