2025 · Paper 1 · Chemistry
Question 2
The printed question, the official key, and each model’s JSON answer plus the reasoning it wrote.
Q02
Official A
Model answers
Claude Fable 5.1
Anthropic
A
Claude Fable 5.1 reasoning
Wavelength maximum (λmax) of the d–d absorption band is inversely related to the crystal field splitting energy Δ₀ (λ = hc/Δ₀). So the stronger the field ligand, the shorter the λmax. Spectrochemical series (relevant ligands): CN⁻ > NH₃ > H₂O > Cl⁻ Field strength order of the complexes: [Co(CN)₆]³⁻ > [Co(NH₃)₆]³⁺ > [Co(NH₃)₅(H₂O)]³⁺ > [Co(NH₃)₅Cl]²⁺ Hence λmax order (increasing): [Co(CN)₆]³⁻ < [Co(NH₃)₆]³⁺ < [Co(NH₃)₅(H₂O)]³⁺ < [Co(NH₃)₅Cl]²⁺ This matches option (A).
GPT 6 Astra
OpenAI
A
GPT 6 Astra reasoning
No written reasoning was returned for this item.
GPT 5.6 Luna
OpenAI
A
GPT 5.6 Luna reasoning
No written reasoning was returned for this item.