24 Reactions of inorganic compounds in aqueous solutions

Question 1

which is more acidic Fe2+ and Fe3+ ?

Answer 1

Fe3+
because is both smaller and more highly charged than Fe2+ making it more strongly polarising

iron strongly attracts electrons from the oxygen atoms of the water ligands, so weakening the O-H bonds in the water molecule. The complex ion will then readily release an H+ ion making the solution more acidic

this is the same for all transition metals

Question 2

distinguishing iron ions

Answer 2

both Fe2+ and Fe3+ exist in aqeuous solution as octahedral hexa-aqua ions. [Fe(H20)6]3+ is pale brown and [Fe(H20)6]2+ is pale green.
when they are dilute it is difficult to tell the difference
add dilute alkali and the colours become a lot clear

Question 3

Amphoteric hydroxide

Answer 3

shows both acid and alkali properties

Question 4

which is a better ligand water or ammonia

Answer 4

ammonia is a better ligand because the lone pair on the nitrogen atom of ammonia is less strongly held than that on the electronegative oxygen atom