[THC]

Sorry, the other thread got locked. This time, I'll write my considerations.

Question: Which one of the following is the best reducing agent, and why:
CO2, NO2, SiO2, SO2

Afaik, they're all +4 due to O's 2*-2. Furthermore, the oxidation number of the free molecules must be 0 for S2, C, Si and N2. So, my answer would be: all of them?

[Borek]

Think in terms of oxidtation state of central atom. What possible oxidation states for Si? For C? S? N? What other oxides of these elements you know?

[THC]

Thanks, so the best reducing agent is SO2?

[IITian]

Indeed!

[THC]

Thank you for answering.