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The complex [Fe(phen)2(NCS)2] undergoes spin crossover at 175K. The statement which is not correct for it is:
  • a)
    Its magnetic moment changes abruptly near 175K
  • b)
    At any temperature lower than 175K, its splitting energy (Δ0) > pairing energy (P)
  • c)
    The compound is high-spin paramagnetic at any temperature lower than 175K.
  • d)
    For this compound the energy difference between Δ0 and P is small
Correct answer is option 'C'. Can you explain this answer?
Most Upvoted Answer
The complex [Fe(phen)2(NCS)2] undergoes spin crossover at 175K. The st...
  • The complex [Fe(phen)2(NCS)2] undergoes spin crossover from the LS state (n=0) at low temperatures to the HS state (n=4) at high temperatures.
  • Therefore, at 250 K, the complex is mostly in the LS state, while at 175K, it is mostly in the HS state.
  • -At 250 K, CFSE = -0.4(0)(Δo) = 0 and eff = μs = √0(0+2)BM = 0 BM
  • - At 175 K, CFSE = -0.4(4)(Δo) = -1.6Δo and eff = μLSx + μHS(1-x) = √0(0+2)x + √4(4+2)(1-x) = 4.90 BM
  • Its magnetic moment changes abruptly near 175K
  • At  175K, it is mostly in the HS state. and HS its splitting energy (Δ0) > pairing energy (P)
The compound is high-spin paramagnetic at any temperature lower than 175K  will the wrong statement.
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Community Answer
The complex [Fe(phen)2(NCS)2] undergoes spin crossover at 175K. The st...
Explanation:

High-Spin Paramagnetic:
At any temperature lower than 175K, the complex [Fe(phen)2(NCS)2] undergoes spin crossover, transitioning from a high-spin state to a low-spin state. This means that at temperatures below 175K, the compound is in a low-spin state and not high-spin paramagnetic as mentioned in option 'C'.

Splitting Energy vs. Pairing Energy:
In the low-spin state of the complex, the splitting energy (Δ0) is greater than the pairing energy (P), which is characteristic of a low-spin configuration. This is in accordance with option 'B' stating that at temperatures below 175K, the splitting energy is greater than the pairing energy.

Change in Magnetic Moment:
As the complex undergoes spin crossover at 175K, its magnetic moment changes abruptly at this temperature. This aligns with option 'A' which states that the magnetic moment changes near 175K.

Energy Difference:
For this compound, the energy difference between the splitting energy (Δ0) and the pairing energy (P) is small in the low-spin state. This supports option 'D' which mentions that the energy difference between Δ0 and P is small for this compound.
In conclusion, the correct statement is that the compound [Fe(phen)2(NCS)2] is not high-spin paramagnetic at any temperature lower than 175K due to its transition to a low-spin state during spin crossover.
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The complex [Fe(phen)2(NCS)2] undergoes spin crossover at 175K. The statement which is not correct for it is:a)Its magnetic moment changes abruptly near 175Kb)At any temperature lower than 175K, its splitting energy (Δ0) > pairing energy (P)c)The compound is high-spin paramagnetic at any temperature lower than 175K.d)For this compound the energy difference betweenΔ0and P is smallCorrect answer is option 'C'. Can you explain this answer?
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The complex [Fe(phen)2(NCS)2] undergoes spin crossover at 175K. The statement which is not correct for it is:a)Its magnetic moment changes abruptly near 175Kb)At any temperature lower than 175K, its splitting energy (Δ0) > pairing energy (P)c)The compound is high-spin paramagnetic at any temperature lower than 175K.d)For this compound the energy difference betweenΔ0and P is smallCorrect answer is option 'C'. Can you explain this answer? for UGC NET 2024 is part of UGC NET preparation. The Question and answers have been prepared according to the UGC NET exam syllabus. Information about The complex [Fe(phen)2(NCS)2] undergoes spin crossover at 175K. The statement which is not correct for it is:a)Its magnetic moment changes abruptly near 175Kb)At any temperature lower than 175K, its splitting energy (Δ0) > pairing energy (P)c)The compound is high-spin paramagnetic at any temperature lower than 175K.d)For this compound the energy difference betweenΔ0and P is smallCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for UGC NET 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for The complex [Fe(phen)2(NCS)2] undergoes spin crossover at 175K. The statement which is not correct for it is:a)Its magnetic moment changes abruptly near 175Kb)At any temperature lower than 175K, its splitting energy (Δ0) > pairing energy (P)c)The compound is high-spin paramagnetic at any temperature lower than 175K.d)For this compound the energy difference betweenΔ0and P is smallCorrect answer is option 'C'. Can you explain this answer?.
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