2025 · Paper 2 · Chemistry
Question 1
The printed question, the official key, and each model’s JSON answer plus the reasoning it wrote.
ChemistryPaper 2Single correct
Q01
Official A
Model answers
Claude Fable 5.1
Anthropic
Correct3 / 3
A
Claude Fable 5.1 reasoning
Sodium nitroprusside test for sulphide ion: Na₂[Fe(CN)₅NO] + Na₂S → Na₄[Fe(CN)₅NOS] (purple/violet colour) The sulphide ion attacks the nitrosyl (NO⁺) ligand, converting it into a thionitrite ligand, NOS⁻ (i.e., NO bonded to S, coordinated to Fe through N). The complex formed is [Fe(CN)₅(NOS)]⁴⁻, which is responsible for the characteristic purple/violet colour. Thus the ligand NO⁺ is converted to NOS⁻.
GPT 6 Astra
OpenAI
Correct3 / 3
A
GPT 6 Astra reasoning
No written reasoning was returned for this item.
GPT 5.6 Luna
OpenAI
Correct3 / 3
A
GPT 5.6 Luna reasoning
No written reasoning was returned for this item.