DP Chemistry Questionbank

What is the correct explanation for the colour of [Cu(H₂O)₆]²⁺?

A. Light is absorbed when an electron moves to a d orbital of higher energy.

B. Light is released when an electron moves to a d orbital of higher energy.

C. Light is absorbed when electrons move from the ligands to the central metal ion.

D. Light is absorbed when electrons move between d and s orbitals.

The oxidation state of cobalt in the complex ion [Co(NH₃)₅Br]^x is +3. Which of the following statements are correct?

I.   The overall charge, x, of the complex ion is 2+.
II.  The complex ion is octahedral.
III. The cobalt(III) ion has a half-filled d-subshell.

A.  I and II only

B.  I and III only

C.  II and III only

D.  I, II and III

Outline why transition metals form coloured compounds.

Explain why iron forms many different coloured complex ions.

The electron configuration of copper makes it a useful metal.

Explain why a copper(II) solution is blue, using section 17 of the data booklet.

[CoCl₆]^3– is orange while [Co(NH₃)₆]³⁺ is yellow. Which statement is correct?

A. [CoCl₆]^3– absorbs orange light.

B. The oxidation state of cobalt is different in each complex.

C. The different colours are due to the different charges on the complex.

D. The different ligands cause different splitting in the 3d orbitals.

Deduce, giving a reason, which complex ion [Cr(CN)₆]³⁻ or [Cr(OH)₆]³⁻ absorbs higher energy light. Use section 15 of the data booklet.

[Cr(OH)₆]³⁻ forms a green solution. Estimate a wavelength of light absorbed by this complex, using section 17 of the data booklet.

Copper is a transition metal that forms different coloured complexes. A complex [Cu(H₂O)₆]²⁺(aq) changes colour when excess Cl⁻(aq) is added.

Explain the cause of this colour change, using sections 3 and 15 from the data booklet.

Copper(II) ion solutions are blue. Suggest, giving your reason, a suitable wavelength of light for the analysis.

Why is hydrated copper (II) sulfate blue?

A.  Blue light is emitted when electrons return to lower d-orbitals.

B.  Light complimentary to blue is absorbed when electrons return to lower d-orbitals.

C.  Blue light is emitted when electrons are promoted between d-orbitals.

D.  Light complimentary to blue is absorbed when electrons are promoted between d-orbitals.

[Cr(OH₂)₆]³⁺ is violet and [Cr(NH₃)₆]³⁺ is yellow. What is correct?

The Colour Wheel

Mg(OH)⁺ is a complex ion, but Mg is not regarded as a transition metal. Contrast Mg with manganese, Mn, in terms of one characteristic chemical property of transition metals, other than complex ion formation.

Explain why, when ligands bond to the iron ion causing the d-orbitals to split, the complex is coloured.

Identify the colour of the emission spectrum of lithium using section 17 of the data booklet.

Describe how the blue colour is produced in the Cu(II) solution. Refer to section 17 of the data booklet.

Examine the relationship between the Brønsted–Lowry and Lewis definitions of a base, referring to the ligands in the complex ion [CuCl₄]²⁻.

Deduce why the Cu(I) solution is colourless.