reactions of ions in aqueous solution

Question 1

what type of metal aqua ions will be the most acidic in solution

Answer 1

small, highly charged cations are the most acidic in solution

Question 2

give an equation for the complete hydrolysis of [M(H2O)6]3+

Answer 2

[M(H2O)6]3+ + 3H2O [M(H2O)3(OH)3] + 3H3O+

Question 3

give the overall reaction for the hydrolysis of [M(H2O)6]2+

Answer 3

[M(H2O)6]2+ + 2OH- [M(H2O)4(OH)2] + 2(H2O)

Question 4

what are the two possible bonds in a metal hexaaquaion that could be broken

Answer 4

• a coordinate bond. the bond holding the ligands to the central metal ion
• a covalent bond. the bonds within the ligand e.g. the covalent bond holding together the oxygen and the hydrogen in H2O

Question 5

what are the products of the equation for

[Fe(H2O)6]2+ + 6NH3

Answer 5

–> [Fe(NH3)6]2+ + 6H2O

Question 6

as the polarising power of the metal ion increases,

Answer 6

there is a greater attraction for the electrons from the O in the water molecule. This makes the O-H bond weaker and easier to break. Breaking the O-H bond releases H+ ions which form H3O+ with water, increasing acidity

Question 7

write a general equation for the hydrolysis of a metal aquaion with a 2+ charge, with sodium carbonate

Answer 7

[M(H2O)6]2+ + CO3 2- MCO3 + 6H2O

Question 8

write a general equation for the same reaction, with a metal ion with a 3+ charge

Answer 8

2[M(H2O)]3+ + 3(CO3)2- 2[M(H2O)3(OH)3] + 3CO2 + 3H2O

Question 9

write a general equation for the reaction of a metal aquaion with a 2+ charge, with ammonia

Answer 9

[M(H2O)6]2+ + 2(NH3) [M(H2O)4(OH)2] + 2NH4+

Question 10

write an equation for the same reaction, with a metal ion with a 3+ charge. Assume ammonia is not in excess.

Answer 10

[M(H2O)6]3+ + 3NH3 [M(H2O)3(OH)3] + 3NH4+

Question 11

what would be the equation is the ammonia was added in excess, with a Cu2+ ion

Answer 11

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

Ligand substitution will only occur when excess ammonia is added to a solution of Cu2+ ions

Question 12

what does amphoteric character describe

Answer 12

the ability of metal hydroxides to react with both acids and alkalis

Question 13

give an equation for the reaction of copper hexaaquaions with HCl

Answer 13

[Cu(H2O)6]2+ + 4Cl- –> [CuCl4]2- + 6H2O

Question 14

give the colour of the following solutions:

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

Answer 14

1) Blue solution
2) green solution ( if left standing, oxidation will occur, forming 3+ ions, and a brown ppt will form)
3) violet solution
4) colourless solution