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Starter. 2. Complete the electronic arrangement of the Co 2 + ion. (1 mark) [Ar] 3. Explain why complex ions with partially filled d sub-levels are usually coloured. ( 2 marks) 4. What is meant by the term co-ordinate bond ?. Starter.

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Starter

2. Complete the electronic arrangement of the Co2+ ion. (1 mark)

[Ar]

3. Explain why complex ions with partially filled d sub-levels are usually coloured. ( 2 marks)

4.What is meant by the term co-ordinate bond?


Starter

2. Complete the electronic arrangement of the Co2+ ion. (1 mark)

[Ar]3d7

3. Explain why complex ions with partially filled d sub-levels are usually coloured. ( 2 marks)

Electrons excited / transition from ground state to excited state (1)Energy absorbed from visible / light (spectrum) (1)


  • 4.What is meant by the term co-ordinate bond?

  • Shared or pair of electronsCome from one atom (1)


Variable oxidation states of transition metals.

L.O.:

Determine the concentration of iron (II) ions in aqueous solutions.

Explain the conditions required to obtain Cr2+.

Homework: Q6 &7 from wiki


PSA10 part 1


Sc

Ti

V

Cr

Mn

Fe

Co

Ni

Cu

Zn

+7

+6

+6

+6

+5

+5

+5

+5

+5

+4

+4

+4

+4

+4

+4

+4

+3

+3

+3

+3

+3

+3

+3

+3

+2

+2

+2

+2

+2

+2

+2

+2

+2

+1


Fe(II)

Iron exists in two common oxidation states, +2 (Fe2+) and +3 (Fe3+).

In aqueous solution, the Fe is readily oxidized from Fe2+ to Fe3+:

Fe2+(aq)  Fe3+(aq) + e

How could you determine the concentration of iron(II) in solution?

Redox titration using Cr2O72-

Redox titration using MnO4-


Task:

Write a balance equation for the reaction of acidified potassium dichromate(VI) with Fe(II)


2CrO42-(aq) + 2H+(aq)  Cr2O72-(aq) + H2O(l)

Which Cr(VI) compound is more stable in acid?


Redox Chemistry of Cr

Cr(III) is more stable than Cr(II)

  • How could you oxidise Cr(II) to Cr(III)?

    By oxygen

    Which conditions are need for Zn to reduce Cr(III) to Cr(II)?


Describe what you would see, and explain the changes which occur when each of the following solutions is treated with an excess of zinc and hydrochloric acid in an apparatus which excludes air.

  • Potassium Dichromate (VI) (5 marks)

    the Cr(VI) is reduced

    to +3

    which is green

    and then +2

    which is blue(5)


Variable oxidation states of transition metals.

L.O.:

Determine the concentration of iron (II) ions in aqueous solutions.

Explain the conditions required to obtain Cr2+.

Homework: Q6 &7 from wiki


Why do oxidations of transition metals tend to happen in alkaline solutions?


In ammoniacal solution, Co2+ ions can be oxidised by oxygen in the air.


  • 5.4 EXERCISE 3 – Variable oxidation states and catalysis


Variable oxidation states of transition metals.

L.O.:

How can the concentration of iron(II) ions in aqueous be found?

How can chromium (II) ions be oxidised?

How can cobalt(II) ions be oxidised?


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