Why exactly does blue litmus paper turn red when it touches acidic solutions?

Question

I tried searching on the web, but they don't say exactly why acid causes blue litmus paper to turn red. Have you guys got any idea? Any help would be appreciated!

Along with it, you can also answer why red litmus paper turns blue when it touches basic solutions.

Answer 1

azolitmin (the active ingredient of litmus paper) is the reason, it turns red when there are lots of extra hydrogen ions floating around (an acid)

it turns bluewhen those combine with oxygen to form OH molecules (ions)

It's just a property of this particular dye that changed color at different pH. Another example is "invisible ink."

Another chemical reaction that causes color change is not reversible, the bleaching caused by chlorine.

Answer 2

As I have come to understand it, I believe, essentially, you are placing the reaction on the paper. Thus, the paper being a dye, the reaction causes a change in the 'litmus' molecule itself, removing (acid) or adding a proton (base), and causing a reversible reaction that brings out the color of the dye. Same for base.

Answer 3

Well I imagine that the situation would be such that the paper is coated with a basic solution that works in the same manner at phenyphthaline. The same solution would be used for the red to blue paper, except it would be in its acidic form.