A-Level Chemistry (OCR) > 3.3 Qualitative Analysis > Flashcards

3.3 Qualitative Analysis Flashcards

Identify ions and compounds using qualitative tests, observations, and chemical reasoning. (39 cards)

Study These Flashcards
1
Q

What type of ion is formed when transition metal ions dissolve in water?

A

Metal-aqua ion

Water molecules act as ligands forming complexes such as [M(H2O)6]2+.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What ligand surrounds metal ions in aqueous transition-metal complexes?

A

Water

Six water molecules usually coordinate to the metal ion.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Fill in the blank:

The complex ion formed when Fe2+ dissolves in water is Fe(H2O)6.

A

2+

This is an octahedral metal-aqua complex.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

True or False:

The acidity of [M(H2O)6]3+ ions is greater than that of [M(H2O)6]2+ ions.

A

True

Higher charge density polarises the O–H bonds more strongly.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What property explains why [M(H2O)6]3+ ions are more acidic than [M(H2O)6]2+ ions?

A

Higher charge density

Greater charge/size ratio weakens O–H bonds in coordinated water.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

True or False:

Aluminium hydroxide dissolves in both acids and bases.

A

True

This demonstrates amphoteric behaviour.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Fill in the blank:

A substance that reacts with both acids and bases is described as _______.

A

amphoteric

Examples include Al(OH)3.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What reagent forms a blue precipitate with Cu2+ ions in solution?

A

Sodium hydroxide

Cu2+ forms a blue Cu(OH)2 precipitate.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

True or False:

Fe2+ ions form a green precipitate when reacting with hydroxide ions.

A

True

Fe(OH)2 appears green but turns brown when oxidised.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Fill in the blank:

Fe3+ ions react with hydroxide ions to form a _______ precipitate.

A

brown

The precipitate formed is Fe(OH)3.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What reagent can dissolve aluminium hydroxide precipitate to form a colourless solution?

A

Excess sodium hydroxide

The amphoteric hydroxide dissolves forming a complex ion.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What laboratory method uses these reactions to identify transition metal ions?

A

Test-tube reactions

Observing colour changes and precipitates helps identify ions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the colour of [Fe(H₂O)₆]²⁺(aq)?

A

Green solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the colour of [Cu(H₂O)₆]²⁺(aq)?

A

Blue solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the colour of [Fe(H₂O)₆]³⁺(aq)?

A

Pale violet solution

appears orange due to hydrolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the colour of [Al(H₂O)₆]³⁺(aq)

Study These Flashcards
A

Colourless solution

17
Q

What happens when NaOH(aq) is added dropwise to [Fe(H₂O)₆]²⁺(aq)?

Study These Flashcards
A

[Fe(H₂O)₄(OH)₂] forms

green precipitate, darkens on standing due to oxidation to [Fe(H₂O)₃(OH)₃]

18
Q

What happens when NaOH(aq) is added dropwise to [Cu(H₂O)₆]²⁺(aq)?

Study These Flashcards
A

[Cu(H₂O)₄(OH)₂] forms

blue precipitate

19
Q

What happens when NaOH(aq) is added dropwise to [Al(H₂O)₆]³⁺(aq)?

Study These Flashcards
A

Al(H₂O)₃(OH)₃] forms

(white precipitate)

20
Q

What happens when NaOH(aq) is added dropwise to [Fe(H₂O)₆]³⁺(aq)?

Study These Flashcards
A

[Fe(H₂O)₃(OH)₃] forms

brown precipitate

21
Q

What happens when excess NaOH(aq) is added to [Fe(H₂O)₆]²⁺(aq)?

Study These Flashcards
A

No further reaction

22
Q

What happens when excess NaOH(aq) is added to [Cu(H₂O)₆]²⁺(aq)?

Study These Flashcards
A

No further reaction

23
Q

What happens when excess NaOH(aq) is added to [Fe(H₂O)₆]³⁺(aq)?

Study These Flashcards
A

No further reaction

24
Q

What happens when NH₃(aq) is added dropwise to [Fe(H₂O)₆]²⁺(aq)?

Study These Flashcards
A

Fe(H₂O)₄(OH)₂] forms

(green precipitate, darkens on standing)

25
What happens when **NH₃(aq)** is added **dropwise** to **[Cu(H₂O)₆]²⁺(aq)**?
[Cu(H₂O)₄(OH)₂] forms ## Footnote (blue precipitate)
26
What happens when **NH₃(aq)** is added **dropwise** to **[Fe(H₂O)₆]³⁺(aq)**?
[Fe(H₂O)₃(OH)₃] forms ## Footnote (brown precipitate)
27
What happens when **NH₃(aq)** is added **dropwise** to **[Al(H₂O)₆]³⁺(aq)**?
[Al(H₂O)₃(OH)₃] forms ## Footnote (white precipitate)
28
What happens when **excess NH₃(aq)** is added to **[Fe(H₂O)₆]²⁺(aq)**?
No further reaction
29
What happens when **excess NH₃(aq)** is added to **[Cu(H₂O)₆]²⁺(aq)**?
[Cu(H₂O)₂(NH₃)₄]²⁺ forms ## Footnote (deep blue solution)
30
What happens when **excess NH₃(aq)** is added to **[Fe(H₂O)₆]³⁺(aq)**?
No further reaction
31
What happens when **excess NH₃(aq)** is added to **[Al(H₂O)₆]³⁺(aq)**?
No further reaction
32
What happens when **Na₂CO₃(aq)** is added to **[Fe(H₂O)₆]²⁺(aq)**?
FeCO₃ forms ## Footnote (green precipitate)
33
What happens when **Na₂CO₃(aq) is added to [Cu(H₂O)₆]²⁺(aq)**?
CuCO₃ forms ## Footnote (blue-green precipitate)
34
What happens when **Na₂CO₃(aq) is added to [Fe(H₂O)₆]³⁺(aq)**?
[Fe(H₂O)₃(OH)₃] forms + CO₂ gas (brown precipitate & bubbles) ## Footnote (brown precipitate & bubbles)
35
What happens when **Na₂CO₃(aq)** is added to **[Al(H₂O)₆]³⁺(aq)**?
[Al(H₂O)₃(OH)₃] forms + CO₂ gas ## Footnote (white precipitate & bubbles)
36
Why do [Fe(H₂O)₆]³⁺ and [Al(H₂O)₆]³⁺ form **hydroxides with CO₃²⁻**?
High charge density polarises CO₃²⁻ leading to hydrolysis → CO₂ + OH⁻ formed → hydroxide precipitate
37
Why does **[Al(H₂O)₃(OH)₃] dissolve in excess NaOH**?
It is amphoteric and forms [Al(H₂O)₂(OH)₄]⁻
38
Why does **[Cu(H₂O)₆]²⁺ form a deep blue solution in excess NH₃**?
Ligand substitution forms [Cu(H₂O)₂(NH₃)₄]²⁺
39
Why does **[Fe(H₂O)₄(OH)₂] darken on standing**?
It is oxidised to [Fe(H₂O)₃(OH)₃] by oxygen in air
A-Level Chemistry (OCR)
flashcards
Decks in class (28)
# Cards
Brainscape helps you reach your goals faster, through stronger study habits.
© 2026 Bold Learning Solutions. Terms and Conditions