Along with what DrBob said, keep in mind that a more reactive metal will lose electrons (and thus become ions) when in the presence of a less reactive metal. These less reactive metals (the chart on wikipedia shows them as at the bottom) will thus steal any electrons needed in...
Is the marshmellow losing heat (exothermic) or absorbing heat (endothermic? Is it losing energy (exothermic) or using energy (endothermic)? Does the process of a marshmellow burning produce energy (exothermic) or require energy (endothermic)? Some things to think about.
How did Dr.Bob find n = 0.0416 mols ?