H2 is a reducing agent, MgO is an oxidizing agent.
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Reactants:
MgO – Magnesium oxide
Other names: Magnesia, Periclase, Magnesium oxide fume
Appearance: White powder ; Hygroscopic fine white powder ; Finely divided white particulate dispersed in air. [Note: Exposure may occur when magnesium is burned, thermally cut, or welded upon.]