In a disproportionation reaction, the disproportionate substance has exactly one oxidation state.
has exactly two oxidation states.
has at least three oxidation states.
has either one or two oxidation states.

> b takes place in the gas phase in an isothermal tubular reactor. the feed is one mole of a per one mole of c, an inert. the entering temperature and pressure are 427°c and 10 atm, respectively. the gas constant r = 0.08206 atm · l/mol · k.