Gas magnetism: choose the incorrect statement regarding paramagnetism of common gases and its use in analysis.

Introduction / Context:
Paramagnetic oxygen analyzers exploit the magnetic susceptibility of O2 to determine its concentration in gas streams. Differentiating paramagnetic and diamagnetic gases is essential for correct analyzer selection and interpretation.

Given Data / Assumptions:

• Paramagnetism arises from unpaired electrons.
• O2 (triplet ground state), NO, and NO2 are paramagnetic; many others are diamagnetic.
• Magnetic susceptibility typically falls with increasing temperature (Curie-type behavior).

Concept / Approach:
CO2 is diamagnetic (all electrons paired), so calling it the strongest paramagnetic gas is false. Paramagnetic analyzers often measure torque or pressure differences produced by O2 in a non-uniform magnetic field, enabling accurate O2 measurements over wide ranges.

Step-by-Step Solution:
Identify known paramagnetic gases: O2, NO, NO2.Recall CO2: diamagnetic → weakly repelled by magnetic fields.Apply temperature effect: higher T → reduced susceptibility for paramagnets.Conclude: statement about CO2 being strongly paramagnetic is wrong.

Verification / Alternative check:
Instrument datasheets for paramagnetic O2 analyzers specify selectivity for O2 over diamagnets like N2 and CO2; cross-sensitivity corrections for NO/NO2 may be noted due to their paramagnetism.

Why Other Options Are Wrong:

• Option a: correct—those gases are paramagnetic.
• Option c: correct—susceptibility decreases with temperature.
• Option d: correct—principle enables paramagnetic analyzers.

Common Pitfalls:
Assuming “acidic” or “heavy” gases are paramagnetic; magnetism depends on electronic structure, not chemical acidity or density.

Final Answer:
CO2 is the strongest paramagnetic gas