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Topic 13 Extra Practice
1. Define the term ligand.
(1)
2. Explain why the complex [Fe(H2O)6]3+ is coloured.
(3)
3. When concentrated hydrochloric acid is added to a solution containing hydrated copper(II) ions, the
colour of the solution changes from light blue to green. The equation for the reaction is:
[Cu(H2O)6]2+(aq) + 4Cl–(aq) → [CuCl4]2–(aq) + 6H2O(l)
(i)
Explain what the square brackets around the copper containing species represent.
(1)
(ii)
Explain why the [Cu(H2O)6]2+ ion is coloured and why the [CuCl4]2– ion has a different
colour.
(2)
4. Deduce the oxidation number of cobalt in the following species.
(i)
[Co(H2O)6]2+
(1)
(ii)
Co2(SO4)3
(iii)
[CoCl4]2–
(1)
(1)
5. Explain why copper is considered a transition metal while scandium is not.
(Total 3 marks)
6. Which metal nitrate solution is coloured?
A. Zn(NO3)2(aq)
B. Ni(NO3)2(aq)
C. Mg(NO3)2(aq)
D. Ca(NO3)3(aq)
7. Ligands can form dative covalent bonds with metal ions to form complex ions. Which of the following can act
as a ligand?
I. Cl–
II. NH3
III. H2O
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
8. Cu2+(aq) reacts with ammonia to form the complex ion [Cu(NH3)4]2+. Identify the type of bond formed
between Cu2+ and NH3 and outline how it is formed.
9. Determine the oxidation state of the metal in the following complex ions or coordination compounds:
a) [Co(NH3)6]3+
b) [AuCl2]1+
c) [Pt(NH3)4I2]2+
d) [Fe(CN)6]4e) [Cr(H2O)5Br]Br2
f) [Mn(H2O)6]I2
10. Write the full electron configuration and draw the orbital box diagram of iron in its oxidation state in question
9d) above, and hence, determine the number of unpaired electrons in this state.
11. What is the coordination number of copper in the [Cu(en)2(H2O)2]2+ complex ion?
12. Polydentate ligands can vary in the number of coordination positions they occupy. In the following compound,
identify the polydentate ligand present and indicate the probable number of coordination positions it occupies
[Cr(C2O4)(H2O)4]Br
13. Which of the following would you expect to have the largest ligand field splitting energy (ΔE)?
[Ti(H2O)6]2+
or
[V(H2O)6]3+
14. Which of the following would you expect to absorb the highest energy of visible light?
[Mn(NH3)6]2+
or
[Mn(H2O)6]2+
15. Which of the following would you expect to absorb the longest wavelength of visible light?
K4[Cr(CN)6]
or
K3[Cr(CN)6]
16. The complex ion trans-[Co(NH3)4Cl2]+ absorbs light primarily in the red region of the visible spectrum (λ max =
680 nm).
a. Sketch the absorption spectrum below.
b. What is the color of the complex?
c. If two of the NH3 ligands are replaced by two Cl- ions to form [Co(NH3)2Cl4]+, predict what will
happen to the ligand field splitting energy (ΔE), the λmax, and the possible color(s).