Year 13 IA2 Chemistry Quiz

Answer explanation

Fe, atomic #26, has 26 electrons in the configuration:

1s²2s²2p⁶3s²3p⁶3d⁶4s²

because the complex ion has an overall -4 charge, and there are 6 CN^- ligands, we need the iron cation to have a charge of +2. To get +2, we remove two 4s electrons from iron:

1s²2s²2p⁶3s²3p⁶3d⁶4s⁰

Which of the following is formed by a ligand exchange reaction? (Hint: there are 2 answers)

• [Cu(NH₃)₄(H₂O)₂]²⁺

• Cu(H₂O)₄(OH)₂

• [CuCl₄]^2-

• [Cu(H₂O)₆]²⁺

Which of the following metal complexes has a co-ordination number of 6?

• [CuCl₄]^2-

• [Co(NH₃)₆]³⁺

• Al(H₂O)₃(OH)₃

• [Cr(H₂O)₆]²⁺

Concentrated hydrochloric acid is added to a mixture of Cu(H₂O)₄(OH)₂ and Fe(H₂0)₃(OH)₃. Which of the following complexes cannot form?

• Fe(H₂O)₄(OH)₂

• [Cu(H₂O)₆]²⁺

• [CuCl₄]^2-

• [Fe(H₂O)₅(OH)]²⁺

If light in the red/orange region is absorbed, what color do we see?

• Red
• Orange
• Blue
• Yellow

If light in the violet region is absorbed, what color do we see?

• Violet
• Orange
• Blue
• Yellow

Color of metal complexes are due to the following factors EXCEPT

• Types of ligands
• Nature of transition metal
• Oxidation states
• Type of orbitals

Answer explanation

All transition metals involve the d orbitals.

Why is Ti³⁺ violet in color when it is in water?

• Presence of water ligands causes the splitting of 3d orbitals

• The electron can be excited

• Visible wavelengths of light are emitted into the water.

• Presence of water ligands causes color formation.

Zn²⁺ solution in the presence of water is colorless. Why?

• Presence of ligands causes the splitting of the 3d orbitals.

• There is no splitting of 3d orbitals.

• There are no electrons in the 3d orbitals to absorb energy for a d-d electron transition.

• 3d orbitals are fully filled and no electrons can absorb energy for a d-d electron transition.

Sc³⁺ solution in the presence of water is colorless. Why?

• Presence of ligands causes the splitting of 3d orbitals.

• There is no splitting of 3d orbitals
• There are no electrons in the 3d orbitals to be excited

• The higher energy level is too high for the electron to reach