NO2 - + H2O HNO2 + OH - what is the bronsted acid in thus equation

The Brønsted acid is a compound which is capable to transfer a proton to any other compound. A proton is a nuclear particle with a positive electrical charge and it is represented by the symbol H⁺ because it constitutes the nucleus of a hydrogen (which is composed by one proton) atom without the electrons. Therefore, in the example given by the question, the water have a Brønsted acid character because it gives the proton (red color) to the nitrogen oxide.