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The structures of two aqueous iron complexes are represented in the diagram - HSC - SSCE Chemistry - Question 36 - 2011 - Paper 1
Question 36
The structures of two aqueous iron complexes are represented in the diagram. Account for the different colours of the complexes. Identify ONE cation and ONE anion ... show full transcript
Worked Solution & Example Answer:The structures of two aqueous iron complexes are represented in the diagram - HSC - SSCE Chemistry - Question 36 - 2011 - Paper 1
Step 1
Account for the different colours of the complexes.
Answer
The different colours of the iron complexes can be primarily attributed to their oxidation states and the ligands coordinated to the iron ion. The green complex corresponds to Fe²⁺ and the yellow-brown complex corresponds to Fe³⁺.
The electronic transition of d-electrons in these complexes involves absorption of specific wavelengths of light. The Fe²⁺ (green complex) has a different electron configuration compared to Fe³⁺ (yellow-brown complex), which causes different energies of d-d transitions, resulting in the absorption of different wavelengths of light and thus produces different colours.
Step 2
Identify ONE cation and ONE anion that can be represented by the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶.
Answer
ONE cation: Na⁺ (Sodium ion) ONE anion: Cl⁻ (Chloride ion)
The cation Na⁺ is formed when sodium loses one electron, while Cl⁻ is formed when chlorine gains one electron, thus both achieving a full outer shell, represented by the electron configuration.
Step 3
Explain the fact that Group I and Group II metal ions have one oxidation state while transition metals often have multiple oxidation states.
Answer
Group I and II metal ions have fixed oxidation states due to their electron configurations. Group I metals lose one electron to achieve a noble gas configuration, resulting in a +1 oxidation state. Group II metals lose two electrons for a +2 oxidation state.
In contrast, transition metals have d-electrons that can participate in bonding and can lose different numbers of electrons, resulting in multiple oxidation states. This variability arises from the ability to lose 2 electrons from the s orbital and varying numbers from the d orbitals, leading to various stable oxidation states.
Step 4
Describe a method by which the values in the table may have been obtained.
Answer
Values in the table may have been obtained using spectroscopy techniques where light is emitted from a source and passed through a prism or diffraction grating. By measuring the wavelength of emitted radiation, corresponding spectral lines can be recorded, providing the wavelengths as seen in the table.
Step 5
Draw an energy level diagram that corresponds to the data given.
Answer
To draw the energy level diagram, first indicate a common final energy level as the ground state. Then, illustrate four energy levels corresponding to each wavelength provided.
- For line number 1 (656 nm), draw an arrow from a higher energy to the common level.
- For line number 2 (486 nm), repeat with a different energy transition.
- For line number 3 (434 nm) and line number 4 (419 nm), continue this method indicating each transition clearly with correct arrows and spacing.