Why does concentrated nitric acid drop litmus test solution, with a little heating, show both the acidity of nitric acid and the oxidation of nitric acid?

Concentrated nitric acid drops into Shi Lei test solution, which turns red first, indicating that it is acidic.

After that, Shi Lei will fade because of the strong oxidation of concentrated nitric acid. In fact, this is also called bleaching in chemistry.

There are two kinds of chemical bleaching, one is oxidation bleaching and the other is compound bleaching.

Among them, concentrated nitric acid, a strong oxidizing substance, is oxidative bleaching, so here it is oxidation.

As you will know later, the fading of SO _ 2 and magenta solution belongs to compound bleaching.

If you don't understand, ask again.