[Capital]

In the process of smelting, at high temperatures of greater than 400^C, I thought the reaction that occurs is
C + PbO --> Pb + CO

However, this site: http://chemcases.com/tel/tel-d.htm says the reaction that forms is C + PbO --> Pb + CO2 because this reaction is spontaneous.

Which one is correct? I think the first one is correct because the high temperature would make the first reaction spontaneous. Is my thinking correct? Thanks for any help.

[curiouscat]

What about

PbO + CO --> Pb + CO2

[Capital]

What about

PbO + CO --> Pb + CO2

Does that reaction occur in the process of smelting?

I thought that reaction only occurs when you want a reaction to be spontaneous. With the extra energy already in the system, the reaction on PbO + C --> PbO + CO would already occur.

On wikipedia, (I know about the accuracy) the process of smelting of lead is described below:
2 PbS + 3 O2 → 2 PbO + 2 SO2
PbO + C → Pb + CO

I don't see why the CO would have to be converted into CO2 if the reaction already has a positive delta G value.

[Arkcon]

What about

PbO + CO --> Pb + CO2

Does that reaction occur in the process of smelting?

Most definitely.  Carbon monoxide produced by incomplete combustion is a powerful reducer for the production of iron, as an example.  As you've realized, the likelihood of the various reactions before you will depend, at least partly, by their deltaG.