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Please tell me how a pH paper works. How does it decide whether the solution is an acid or a base on the basis of ions formed and how it can determine its concentration. How does it indicate an acid or a base?

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marked as duplicate by Jon Custer, Todd Minehardt, Freddy, ringo, Nanoputian May 14 '16 at 10:44

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It's a piece of paper with one or a couple of these coated on it: https://en.wikipedia.org/wiki/PH_indicator

Indicators are dye molecules that change colour depending on the pH of a solution.

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    $\begingroup$ Perhaps you could provide a little more detail here about how this works? At the moment this is in danger of being flagged as low quality for being too brief. $\endgroup$ – bon May 13 '16 at 14:29

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