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Chemistry > 3.2.6 - Reaction of ions in aqueous solutions > Flashcards

3.2.6 - Reaction of ions in aqueous solutions Flashcards

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1
Q

How do hydrated metal ions exist?

A

as hexaaqua complexes

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2
Q

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

A

<font><b>Green</b></font>

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3
Q

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

A

<font><b>Blue</b></font>

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4
Q

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

A

<font><b>Purple</b></font>

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5
Q

Why are hexaaqua complexes stabilised?

A

Charge is spread

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6
Q

Why can hexa-aqua ions act as acids?

A

<ul><li>Charge on cation attracts <font>electrons</font></li><li>Bonds in the water ligand are <font>weakened</font></li><li>H+ therefore can be removed</li></ul>

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7
Q

Give an equation to show how Iron (II) hexa aqua acts as an acid.

A
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8
Q

M2+ acids are…

A

very weak

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9
Q

What type of reactions do metal-aqua ions undergo when reacting with water?

A

hydrolysis

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10
Q

How do metal-aqua ions react with OH-? Give equations for [M(H2O)6]2+ and [M(H2O)6]3+.

A
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11
Q

What colour is Fe(OH)2?

A

<font><b>Green</b></font>

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12
Q

What colour is Cu(OH)2?

A

<font><b>Blue</b></font>

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13
Q

What colour is Al(OH)3?

A

White

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14
Q

What colour is Fe(OH)3?

A

<font><b>Brown</b></font>

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15
Q

How do hydroxides (formed from hexa-aqua ions) react with acids? Give an example for [Cu(H2O)4(OH)2].

A

react to reform the hexaaqua ions

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16
Q

How does aluminium hydroxide react with xs OH-?

A

<ul><li>It is <b>amphoteric</b></li><li>Forms a hydroxoanion</li><li>(i.e it <b><font>dissolves</font></b>)</li></ul>

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17
Q

How do M2+ ions react with carbonates?

A

Insoluble carbonates form

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18
Q

What colour is FeCO3?

A

<font><b>Green</b></font>

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19
Q

What colour is CuCO3?

A

<font><b>Blue-green</b></font>

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20
Q

How do M3+ ions react with carbonates? Write an equation for [M(H2O)6]3+.

A

<ul><li>Carbonates of oxidation state +3 do not exist</li><li>Hence, acts as a base so hydroxides are formed with CO2 and water</li></ul>

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21
Q

What are the observations for Iron (III) reacting with carbonate?

A

<font><b>Brown ppt </b></font>

and effervescence

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22
Q

What are the observations for Aluminium (III) reacting with carbonate?

A

White ppt and effervescence

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23
Q

What are the colours of the vanadium ions?

A

+5: yellow<br></br>+4: blue<br></br>+3: green<br></br>+2: violet

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24
Q

How do Iron (II), Iron (III) and Aluminium (III) react with NH3 dropwise and excess?

A

Dropwise: forms hydroxide ppts<br></br>Excess: no further change

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25
How do Iron (II), Iron (III) and Copper (II) react with NaOH dropwise and excess?
Dropwise: hydroxide ppts
Excess: No further change (rem aluminium dissolves tho)
26
Amphoteric nature of Aluminium:
![Image](paste-41c0b5fe0af8778124dd96ece5430878ca331b8b.jpg) adding a base: ## Footnote ![Image](paste-a0f8db44d77f108e1db1580ccaf65ce939ae7601.jpg) Acts as a brownsted lowery acid H+ and donates a H+ to react with OH- to dissolve it.
27
What is a Lewis acid?
An electron pair acceptor
28
What is a Lewis Base?
A Electron pair donor
29
Why does Al2O3 form a precipitate that fully dissolves in NaOH?
  • Al2O3 is amphoteric and is the only metal ion that will dissolve in excess NaOH
30
Explain the reaction of ions with Ammonia (NH3)?
  • All metal ions form a white precipitate
  • However copper hydroxide is the only one that completely dissolves when we add excess NH3 as there is ligand substitution
  • Precipitate dissolves where Copper hydroxide forms a dark-blue solution
31
Why does Fe2+ need to be made fresh?
Oxidises readily to form Fe3+
32
Explain the colours of [Fe(H2O)6]2+:
  • In aqueous solution : Green
  • In NH3: Dirty Green Precipitate
  • In Excess NaOH: No change as its insoluble
  • In Excess NH3: No change as Insol.
  • In Sodium Carbonate: Green ppt.
33
Explain the colour change of [Cu(H2O)6]2+:
  1. In Aqueous Solution - Yellow colour
  2. In NH3 - Orange ppt.
  3. In Excess NaOH - No change as insol.
  4. In excess NH3 - No change as insol.
  5. In Sodium Carbonate - Brown ppt.
34
Explain the colour change of [Al(H2O)6]3+:
  1. In Aqueous solution - Colourless
  2. In NH3 - White ppt.
  3. In Excess NaOH - Colourless solution
  4. In Excess NH3 - Insoluble as no change
  5. Sodium carbonate - white ppt
35
Which elements have the largest atomic radius across a period?
The first element.
36
Explain why Copper (I) Iodide is a white solid?
  • Full 3d sub-shell
  • Cannot absorb visible light.
37
Equation for [Cu(NH3)4]2+ in excess NH3:
![Image](paste-02c37d4bede54a8f6dccaa3cbd335fe02d0f7a40.jpg)
38
Copper and Fe reaction with carbonates:
![Image](paste-4e4624ba51debaddf51cbdad72bf00bdf0cc78a1.jpg)
39
Reaction of Fe and Al with carbonates:
![Image](paste-fdf9ff07c2212ca12466f9e423048143ee28e9d5.jpg)
40
Amphoteric Nature of Aluminium:
![Image](paste-e0b73a879e055207944ff52641442ca1575d814d.jpg)
41
Define Lewis acids and bases.
A Lewis acid is an electron pair acceptor, while a Lewis base is an electron pair donor.
42
Describe the formation and colors of metal-aqua ions.
  • Metal-aqua ions like [M(H2O)6]2+ and [M(H2O)6]3+ are formed when metal ions hydrate in aqueous solution.
  • [Fe(H2O)6]2+ is green,
  • [Cu(H2O)6]2+ is blue,
  • [Al(H2O)6]3+ is colorless
  • [Fe(H2O)6]3+ appears yellow/brown due to hydrolysis reactions.
43
What happens when transition metal hydroxides react with excess ammonia?
With excess ammonia, a ligand substitution occurs where ammonia displaces water molecules in the complex.
44
How does aluminum hydroxide demonstrate amphoteric behavior?
Aluminum hydroxide reacts with both acids and bases, showing its amphoteric nature.
45
Explain the different reactions of 2+ and 3+ ions with carbonate ions.
  • 2+ ions such as Cu2+ and Fe2+ react with carbonate ions to form insoluble carbonates.
  • 3+ ions like Al3+ and Fe3+ react to form hydroxide precipitates and evolve CO2 gas.
46
Describe how complex ions form in aqueous solutions with specific ligands.
  • In aqueous solutions, complex ions form when central metal ions bond with ligands such as water, ammonia, or hydroxide.
47
How does charge density affect the hydrolysis of metal ions?
  • Higher charge density in metal ions leads to stronger polarisation of water ligands.
48
Colour of: [Cu(H2O)6]2+
Blue solution
49
Colour of: [Fe(H2O)6]2+
Green solution
50
Colour of: [Al(H2O)6]3+
Colourless solution
51
Colour of: [Co(H2O)6]2+
Pink solution
52
What is the color of [Fe(H2O)6]2+?
Blue solution
53
What is the color of [Al(H2O)6]3+?
Green solution
54
What is the color of [Co(H2O)6]2+?
Colourless solution
55
What is the color of [Co(H2O)6]3+?
Pink solution
56
Why is [M(H2O)6]3+ more acidic than [M(H2O)6]2+?
M3+ has higher charge / more polarising; electrons on O more attracted to M3+; O-H bond breaks more easily.
57
What do you observe when dilute aqueous ammonia is added to copper(II) ions?
Blue precipitate is formed, it then dissolves to form deep blue solution
58
What is the role of iron as a heterogeneous catalyst in the Haber process?
Iron provides a surface for hydrogen and nitrogen to adsorb, weakening their bonds, allowing the reaction to occur. The efficiency and lifetime of the catalyst are affected by its surface area and poisoning by impurities like sulfur.
59
Why is the reaction between peroxodisulfate(VI) ions and iodide ions slow before the catalyst is added?
The reaction is slow because the negative ions repel each other, leading to a high activation energy.
60
How does Fe2+ catalyse the reaction between peroxodisulfate(VI) ions and iodide ions?
Fe2+ catalyzes the reaction by undergoing redox reactions: 2Fe2+ + S2O82− → 2SO42− + 2Fe3+; 2Fe3+ + 2I− → 2Fe2+ + I2.
61
Calculate the maximum volume of hydrogen gas produced when 0.998 g of pure iron reacts with hydrochloric acid.
Moles of Fe: 0.998 / 55.8 = 0.0179; Moles of HCl: 30.0 × 1.00×10−3 = 0.0300; Limiting reagent is HCl; Moles of H2 produced: 0.0300 / 2 = 0.0150; Using PV = nRT, volume V = 0.0150 × 8.31 × 303 / 100,000 = 3.78 × 10−4 m³.
62
Why does an aqueous solution containing [Fe(H2O)6]3+ have a lower pH than one containing [Fe(H2O)6]2+?
Fe3+ ions have a higher charge density and are more polarizing, causing them to weaken the O-H bonds in water ligands more effectively, leading to the release of more H+ ions, resulting in a lower pH.
63
Explain why a solution containing [Al(H2O)6]3+ has a pH less than 7.
[Al(H2O)6]3+ + H2O ↔ [Al(H2O)5(OH)]2+ + H3O+; Al3+ has a high charge density, polarising the O-H bonds in water, releasing H+ ions, thus lowering the pH.

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