Reactions of aqueous ions

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Total cards: 24•Content version: v4•Public deck•Updated: 8/1/2026

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Front (Question)

What is meant by enthalpy of hydration?

Back (Answer)

• standard enthalpy change • when one mole of gaseous ions • covered into one mole of aqueous ions

Front (Question)

enthalpy of hydration is…

Back (Answer)

• always exothermic • bonds made with water molecules

Front (Question)

What is a co-ordinate bond?

Back (Answer)

• shared pair of electrons • that have come from the same atom

Front (Question)

What is a ligand?

Back (Answer)

• ion/molecule with lone pair of electrons • forms co-ordinate bond with transition metal ion

Front (Question)

What is a complex ion?

Back (Answer)

central atom/ion surrounded by ligands

Front (Question)

What is the co-ordination number?

Back (Answer)

number of co-ordinate bonds formed by transition metal ion

Front (Question)

What are the 4 hexa aqua ions?

Back (Answer)

[Fe(H2O)6] 2+ [Fe(H2O)6] 3+ [Cu(H2O)6] 2+ [Al(H2O)6] 3+

Front (Question)

What colour solution does Cu 2+ give when hydrated?

Back (Answer)

[Cu(H2O)6] 2+ (aq) Blue solution

Front (Question)

What colour solution does Fe 2+ give when hydrated?

Back (Answer)

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

#10

Front (Question)

What colour solution does Fe 3+ give when hydrated?

Back (Answer)

[Fe(H2O)6] 3+ (aq) Purple solution may look yellow/brown

#11

Front (Question)

What colour solution does Al 3+ give when hydrated?

Back (Answer)

[Al(H2O)6] 3+ (aq) Colourless solution

#12

Front (Question)

Why are the 3+ ions more acidic?

Back (Answer)

• Fe3+ smaller and more highly charged than Fe2+ • so Fe3+ more polarising • Fe3+ attracts LP on oxygen of water ligands more strongly • weakens O-H bond strength • Fe3+ complex more easily releases H+ • Fe2+ does not release H+

#13

Front (Question)

What is the equation which represents [Fe(H2O)6] 3+ acting as an acid?

Back (Answer)

[Fe(H2O)6] 3+ —> [Fe(H2O)5(OH)] 2+ + H+ OR [Fe(H2O)6] 3+ + H2O —> [Fe(H2O)5(OH)] 2+ + H3O+

#14

Front (Question)

What is the equation which represents [Al(H2O)6] 3+ acting as an acid?

Back (Answer)

[Al(H2O)6] 3+ —> [Al(H2O)5(OH)] 2+ + H+ OR [Al(H2O)6] 3+ + H2O —> [Al(H2O)5(OH)] 2+ + H3O+

#15

Front (Question)

Reaction of [Fe(H2O)6] 2+ with Na2CO3

Back (Answer)

[Fe(H2O)6] 2+ + CO3 2- —> FeCO3 + 6H2O green solution becomes green ppt FeCO3

#16

Front (Question)

Reaction of [Fe(H2O)6] 2+ with NaOH

Back (Answer)

[Fe(H2O)6] 2+ + 2OH- —> [Fe(H2O)4(OH)2] (s) + 2H2O green solution becomes green ppt [Fe(H2O)4(OH)2] (s) • green ppt goes brown on standing in air • oxygen oxidises Fe2+ to Fe3+

#17

Front (Question)

Reaction of [Fe(H2O)6] 2+ with NH3

Back (Answer)

[Fe(H2O)6] 2+ + 2NH3 —> [Fe(H2O)4(OH)2] (s) + 2NH4+ • green solution becomes green ppt [Fe(H2O)4(OH)2] (s) • green ppt goes brown on standing in air • oxygen oxidises Fe2+ to Fe3+

#18

Front (Question)

Reaction of [Cu(H2O)6] 2+ with Na2CO3

Back (Answer)

[Cu(H2O)6] 2+ + CO3 2- —> CuCO3 (s) + 6H2O • blue solution becomes blue/green ppt

#19

Front (Question)

Reaction of [Cu(H2O)6] 2+ with NaOH

Back (Answer)

[Cu(H2O)6] 2+ + 2OH- —> [Cu(H2O)4(OH)2] (s) + 2H2O • blue solution becomes blue ppt [Cu(H2O)4(OH)2] (s)

#20

Front (Question)

Reaction of [Cu(H2O)6] 2+ with NH3

Back (Answer)

[Cu(H2O)6] 2+ + 2NH3 —> [Cu(H2O)4(OH)2] (s) + 2NH4+ • blue solution becomes blue ppt

#21

Front (Question)

Reaction of [Cu(H2O)6] 2+ in excess NH3

Back (Answer)

[Cu(H2O)6] 2+ + 4NH3 —> [Cu(H2O)2(NH3)4] 2+ (aq) + 4H2O • blue solution becomes deep blue solution [Cu(H2O)2(NH3)4] 2+ (aq) [Cu(H2O)6] 2+ + 4NH3 —> [Cu(H2O)2(NH3)4] 2+ (aq) + 2H2O + 2OH- • blue solution becomes deep blue solution [Cu(H2O)2(NH3)4] (aq)

#22

Front (Question)

Reaction of [Cu(H2O)6] 2+ with HCl

Back (Answer)

[Cu(H2O)6] 2+ + 4Cl- —> [CuCl4] 2- (aq) + 6H2O • blue solution —> yellow solution [CuCl4] 2- (aq) • complex changes from octahedral to tetrahedral

#23

Front (Question)

Reaction of [Fe(H2O)6] 3+ with Na2CO3

Back (Answer)

2 [Fe(H2O)6] 3+ + 3CO3 2- —> 2[Fe(H2O)3(OH)3] (s) + 3CO2 + 3H2O yellow/brown solution —> brown ppt and effervescence - CO2 gas evolved

#24

Front (Question)

Reaction of [Fe(H2O)6] 3+ with NaOH

Back (Answer)

[Fe(H2O)6] 3+ + 3OH- —> Fe(H2O)3(OH)3] (s) + 3H2O yellow/brown solution —> brown ppt