practical: identifying inorganic aqueous ions

Question 1

what is the initial colour of [Fe(H₂O)₆]2+

Answer 1

green solution

Question 2

what is the initial colour of [Cu(H₂O)₆] 2+

Answer 2

blue solution

Question 3

what is the initial colour of [Fe(H₂O)₆]3+

Answer 3

brown solution

Question 4

what is the initial colour of [Al(H₂O)₆]3+

Answer 4

colourless solution

Question 5

what colour does each aqeous ion turn when NaOH(aq) dropwise then in excess

Answer 5

[Fe(H₂O)₆]2+ : green ppt of [Fe(H₂O)₄(OH)₂]
in excess: no further change
[Cu(H₂O)₆] 2+ :pale blue ppt of [Cu(H₂O)₄(OH)₂
in excess: no further change
[Fe(H₂O)₆]3+ : brown ppt of [Fe(H₂O)₃(OH)₃]
in excess: no further change
[Al(H₂O)₆]3+ :white ppt of [Al(H₂O)₃(OH)₃]
in excess: ppt dissolves to a colourless solution of [Al(OH)6]-3

Question 6

what colour does each aqeous ion turn when NH3(aq) dropwise then in excess

Answer 6

[Fe(H₂O)₆]2+ : green ppt of [Fe(H₂O)₄(OH)₂]
in excess: no further change
[Cu(H₂O)₆] 2+ :pale blue ppt of [Cu(H₂O)₄(OH)₂
in excess: ppt dissolves to a dark blue solution of [Cu(H₂O)₂(NH₃)₄]2+
[Fe(H₂O)₆]3+ : brown ppt of [Fe(H₂O)₃(OH)₃]
in excess: no further change
[Al(H₂O)₆]3+ :white ppt of [Al(H₂O)₃(OH)₃]
in excess: no further change

Question 7

what colour change does each aqeous ion turn when HCl(aq) is added

Answer 7

[Cu(H₂O)₆] 2+: green solution of [CuCl4]2-
NVC with all the other aqueous ions

Question 8

write the ionic equation for Fe3+ with both NaOH and NH3 and observation

Answer 8

[Fe(H2O)6]3+ + 3OH- ==> [Fe(H2O)3(OH)3] + 3H2O
[Fe(H2O)6]3+ + 3NH3 ==> [Fe(H2O)3(OH)3] + 3NH4+
brown solution ==> brown ppt

Question 9

write the ionic equation for Al3+ with both NaOH and in excess and NH3

Answer 9

[Al(H2O)6]3+ + 3OH- ==> [Al(H2O)3(OH)3] + 3H2O
[Al(H2O)3(OH)3] + 3OH- ==> [Al(OH)6]3- +3H2O
[Al(H2O)3+ + 3NH3 ==> [Al(H2O)3(OH)3] + 3NH4+

Equation 1 and 3: colourless sol to white ppt
equation 2: white ppt to colourless sol

Question 10

write the ionic equation for Fe2+ with both NaOH and NH3

Answer 10

[Fe(H2O)6]2+ + 2OH- ==> [Fe(H2O)4(OH)2] +2H2O
[Fe(H2O)6]2+ + 2NH3 ==> [Fe(H2O)4(OH)2] + 2NH4+
green solution ==> green ppt

Question 11

write the ionic equation for Cu2+ with: NaOH; NH3; and in excess; HCl

Answer 11

[Cu(H2O)6]2+ +2OH- ==> [Cu(H2O)4(OH)2] + 2H2O
[Cu(H2O)6]2+ +2NH3 ==> [Cu(H2O)4(OH)2]+ 2NH4+
[Cu(H2O)4(OH)2] +4NH3 ==> [Cu(H2O)2(NH3)4]2+ +2H2O + 2OH-
[Cu(H2O)6]2+ 4Cl- ==> CuCl4^2- +6H2O

Question 12

what is the final species produced when excess of ammonia is added to aqueous aluminium chloride

Answer 12

[Al(H2O)3(OH)3]