Nitrogen dioxide is an acidic gas and produce an acidic solution in the water (mixture of acids).
Otherwise, we can say, NO2 is one of the strong acidic gas in chemistry.
Nitrogen dioxide is an acidic gas. NO2 dissolves very well in water react with water to give nitrous acid and nitric acid. You can see brown colour of nitrogen dioxide is disappeared when NO2 reacts with water.
This reaction is an oxidizing - reducing reaction and a hydrolysis reaction.
Nitrous(HNO2) and nitric acids(HNO3) are given as products. HNO2 is a weak acid and HNO3 is a strong acid.
Oxidation number of nitrogen in NO2 is +4. Oxidation of nitrogen in HNO2 and HNO3 is +3 and +5 respectively.
NO2 is reduced to HNO2 and oxidized to HNO3.
Now, we NO2 is sent to the water. Check pH value of the solution. You can see pH of the solution is under 7 due to producing of HNO3 and HNO2.
Brown colour NO2 reducing in water, can be used to identify Br2 gas from NO2. Br2 brown colour is not changed much with water. Br2 slightly reacts with water to produce HBr and HOBr. Therefore Br2 brown colour is kept in the water.
Nitrogen dioxide reacts with rain water in the sky to produce acid rain which is a large environmental issue.
Nitrogen dioxide will give nitric acid and nitrous acid in water. Aqueous nitric acid solution shows pH value under 7. If lot of nitrogen dioxide dissolve in water, pH alue can be very low such as 1,2,3 giving strong acidic solution.
Oxidation numbers of carbon and nitrogen atoms in carbon monoxide and nitric oxide are +2 and +2 respectively. When oxidation number is high in oxides of an element, acidic properties increases.