Aqueous Ions

Question 1

Give the formula and colour of hexa aqua Fe2+ ions

Answer 1

[Fe(H2O)6] 2+
Pale green solution

Question 2

Give the formula and colour of hexa aqua Cu2+ ions

Answer 2

[Cu(H2O)6] 2+
Blue

Question 3

Give the formula and colour of a hexa aqua Fe3+ ion

Answer 3

[Fe(H2O)6] 3+
Yellow/brown

Question 4

What is the formula and colour of a hexagon aqua Al3+ ion

Answer 4

[Al(H2O)6] 3+
Clear and colourless

Question 5

What is a bronsten-l lowery acid?

Answer 5

A substance that donates h+ ions

Question 6

What is hydrolysis?

Answer 6

The breaking of bonds using water

Question 7

What happens when a hexa aqua metal ion reacts with water?

Answer 7

There is a hydrolysis reaction
The charge on the metal ion causes the water ligand to be polarised.
If the metal ion have large enough polarising power, the bonds in water ligands are weakened, and they donate a proton to the surrounding water molecules

Question 8

How does pKa determine how acidic a hexa aqua metal ion is?

Answer 8

If pKa is lower, the ion is more acidic and dissociates more and releases more H3O+/H+

Question 9

How does the charge/ size ratio of a hexa aqua metal ion affect its acidity?

Answer 9

If the ion is smaller and highly charged it will be more acidic. Because the metal ion can polarise the water ligands more. The O-H bonds are weakened more readily and the H+ is more easily donated

Question 10

What happens when a base (sodium hydroxide) is added to a hexa aqua metal ion?

Answer 10

An insoluble precipitate of the metal hydroxide is created.
A reversible reaction is created until the metal hydroxide is no longer charged.

Question 11

What is the product and appearance when sodium hydroxide is added to [Fe(H2O)6] 3+ ?

Answer 11

[Fe(H2O)3(OH)3
Brown ppt

Question 12

What is the product and appearance when sodium hydroxide is added to [Al(H2O)6] 3+ ?

Answer 12

[Al(H2O)3(OH)3]
White ppt

Question 13

What does amphoteric mean?

Answer 13

A species that can act as both an acid and a base

Question 14

What is the formula and appearance of aluminium hydroxide?

Answer 14

[Al(H2O)3(OH)3]
White ppt

Question 15

Give the equation for when aluminium hydroxide reacts with an acid, give the appearance of the product

Answer 15

[Al(H2O)3(OH)3] + 3H+ —> [Al(H2O)6] 3+
Clear and colourless solution

Question 16

Give the equation for when aluminium hydroxide reacts with a base, give the appearance of the product

Answer 16

[Al(H2O)3(OH)3] + OH- —> [Al(H2O)2(OH)4]- + H2O
Clear and colourless solution

Question 17

Give the equation for when [Fe(H2O)6]2+ reacts with NaOH , what is the appeared of the product?

Answer 17

[Fe(H2O)6]2+ +2OH- —> [Fe(H2O)4(OH)2] +2H2O
Green ppt

Question 18

What is the general equation and observations for the reaction between NaOH and a metal hexa aqua ion?

Answer 18

[M(H2O)6] 2+ + 2OH- —> [M(H2O)4(OH)2] + 2H2O
A ppt is formed

Question 19

What are the observations between an Fe (II) hexa aqua ion and NaOH?

Answer 19

Goes from a pale green solution to a green ppt

Question 20

What happens when [Fe(H2O)4(OH)2] is left to stand in the air?

Answer 20

Iron hydroxide is oxidised and turns brown

Question 21

What are the observations when copper hexa aqua ion reacts with NaOH?

Answer 21

Goes from a pale blue solution to a blue ppt

Question 22

Why can ammonia react with metal hexa aqua ions?

Answer 22

Because it is a weak base and metal hexa aqua ions are weakly acidic

Question 23

What is the equation and observations when Fe (III) aqua ion reacts with ammonia?

Answer 23

[Fe(H2O)6] 3+ + 3NH3 —> [Fe(H2O)3(OH)3] + 3NH4 +
Yellow/ brown solution to brown ppt

Question 24

What is the equation and observations when Al aqua ion reacts with ammonia?

Answer 24

[Al(H2O)6] 3+ + 3NH3 —> [Al(H2O)3(OH)3] + 3NH4+
Clear and colourless solution to a white ppt

Question 25

What is the equation and observations when Fe (II) aqua ion reacts with ammonia?

Answer 25

[Fe(H2O)6] 2+ + 2NH3 —> [Fe(H2O)4(OH)2] + 2NH4+ Green solution to and green ppt

Question 26

What is the equation sna observations when Cu (II) reacts with ammonia?

Answer 26

[Cu(H2O)6] 2+ + 2NH3 —> [Cu(H2O)4(OH)2] + 2NH4+ Pale blue solution to a blue ppt

Question 27

What happens when an excess of ammonia is added to a Cu (II) hydroxide ppt? What is the equation and observations for this?

Answer 27

A new complex is formed by a ligand substitution reaction [Cu(H2O)4(OH)2] + 4NH3 —> [Cu(H2O)2(NH3)4] 2+ + 2H2O + OH- Blue ppt to deep blue solution

Question 28

What is the overall equation between the Cu (II) hexa aqua ion and excess ammonia?

Answer 28

[Cu(H2O)6] 2+ + 4NH3 —> [Cu(H2O)4(OH)2] + 4H2O

Question 29

What is the general equation and observations for when metal (II) hexa aqua ions react with NaCO3?

Answer 29

[M(H2O)6] 2+ + CO3 2- —> MCO3 + 6H2O Insoluble metal carbonates are formed

Question 30

What is the general equation and observations for when metal (III) hexa aqua ions react with NaCO3?

Answer 30

2[M(H2O)6] 3+ + 3CO3 2- —> 2[M(H2O)3(OH)3] + 3CO2 + 3H2O Metal hydroxides and carbon dioxide is produced, and water

Question 31

Why does Metal (III) hexa aqua ions form hydroxides when reacted with NaCO3 instead of metal carbonates?

Answer 31

They are stronger acids due to their higher charge to size ratio

Question 32

What are the observations when Cu (II), Fe(II), Fe(III) or Al hexa aqua ions react with NaCO3?

Answer 32

Cu(II)- blue/green ppt Fe(II)- green ppt Fe(III)- brown ppt Al- white ptt

Question 34

Give the equation for when EXCESS NaOH reacts with [Al(H2O)6]3+ (e.g aluminium hydroxide is formed, and the reacts with excess NaOH )

Answer 34

[Al(H2O)6]3+ + 4OH- —> [Al(H2O)2(OH)4]- + 4H2O