The gas produced in the diagram above is NO (nitric oxide). This can be determined by the chemical equation for the reaction shown in the diagram:
2NO2(g) + 4H2(g) → 2NH3(g) + 4H2O(g) + 2NO(g)
Since there is no NH3 (ammonia) or N2O4 (dinitrogen tetroxide) in the options, the only gas produced in the reaction that is listed is NO (nitric oxide).
