Metal aqua ions

Question 1

What is a metal aqua complex ions

Answer 1

When water molecules form co-ordinate bonds with metal ions.

• this happens after transition metals dissolve in water.

Question 2

How are metal aqua ions formed?

Answer 2

Water molecules donate a non-bonding pair of electrons from their oxygen.

Question 3

Metal aqua 2+ ions…. ( in water)

acidity reaction

Answer 3

Slightly dissociate in water

Forming a weak acidic solution ( Metal aqua” + ion” and H3o+ )

e.g.

Cu(H2o)6 2+ + H20 -> [Cu(OH)(H2o)5] + + H3o+

reversible reaction
everything (aq) except water (l)

Question 4

Metal aqua 3+ ions…. ( in water)

acidity reaction

Answer 4

Dissociate more than 2+ ions

Forming a stronger acidic solution

Question 5

WHY do metal aqua 3+ ions form a more ACIDIC SOLUTION than 2+ ions?

its the same for 2+ ions, but only 2 steps instead of 3

Answer 5

• Metal 3+ ions have a higher charge density
• so they are more polarising than 2+ ions
• so they attract electrons from the oxygen atoms of the co-ordinated water molecules more strongly, weakening the O-H bond
• More likely that a H+ ion will be released, making the solution more acidic.

Question 6

What does adding OH- ions do to metal aqua 3+ ions

hydrolysis reaction

Answer 6

Removes H3O+ ions

• so equilibrium shifts to the right
• producing more H3O+ ions
• DO THIS 3 TIMES to form an insoluble uncharged metal hydroxide( state symbol will be solid)
• OH goes up by 1 each time H20 goes down by 1

Question 7

What is an example of an amphoteric metal hydroxide?

Answer 7

Aluminium hydroxide.

1) in the presence of a base it acts as a Bronsted Lowry acid and donates H+ ions to OH- ions forming a soluble compound
2) In the presence of an acid it can act as a Bronsted Lowry base and accept H+ ions from H3O+ ions.

Question 8

What happens when ammonia solution dissolves in water general equation:

Answer 8

NH3 + H2O -> NH4 + + OH-

reversible reaction
everything (aq) except (l) h2o

Question 9

Why don’t carbonates displace metal aqua 3+ ions?

Answer 9

This is because there is a higher concentration of H3O + ions

• carbonates react with the H3O+ ions, removing H3O+ ions from the solution, shifting the equilibrium to the right.
• so the precipitate formed is M(OH)3(h2O)3

Question 10

How are you supposed to tell if the sample contains Fe2+ or Fe3+ ions after reacting with sodium carbonate?

Answer 10

sample containing Fe3+ will form bubbles.

- sample containing Fe3+ will not give off gas

Question 11

What is an error that may happen when Fe2+ react with sodium carbonate?

Answer 11

If left to long in the air Fe2+ ions will oxidise into Fe3+ ions.

• to prevent this: Solution should be freshly made.