At about 9: 40 on May 3, 2008, Beijing was hit by a rare thunderstorm, and the sky suddenly darkened, as if night had fallen. In this weather, the air

(1) There was a rare thunderstorm in Beijing, and the sky suddenly darkened, as if night had fallen. In this weather, nitrogen in the air directly combines with oxygen under discharge conditions to generate colorless and insoluble nitric oxide gas. So the colorless gas a is nitric oxide,

So the answer is: nitric oxide; No;

(2) Nitric oxide is insoluble in water and easily combines with oxygen in the air at room temperature to generate reddish-brown nitrogen dioxide gas, so gas B is nitrogen dioxide, NO2 reacts with water, N changes from +4 valence to +5 valence to generate HNO3, and N changes from +4 valence to +2 valence, and the valence decreases to generate NO. The chemical equation is: 3NO2+H2O=2HNO3+NO,

So the answer is: 3NO2+H2O = 2HNO3+No.