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Thursday, January 1, 2015

How does pH paper work?

what is pH?

pH is the negative logarithm  of Hydrogen  ion concentration.

pH = - log[H+]

Higher Hydrogen ion concentration indicates, acidic condition, and Higher Hydroxide ion concentration, indicates basic or alkaline condition.

When there is equal amount of hydrogen ions and hydroxide ions, it indicates neutral condition.
Why pH paper is used?

pH paper is used to determine if a solution is acidic, basic or neutral.

This is determined, by dipping part of the pH paper into a solution of interest, and watching the colour change.

The packages that pH paper comes in, often includes a colour-coded scale indicating the pH that, something has when the paper turns a certain colour.

pH paper and colour

For instance, if the paper turns a dark greenish-blue, the pH may likely be around 11 to 14.

If the paper turns red, the pH may likely be around 1 to 4.

How does pH Paper work?

The pH paper changes colour in different pH solutions is because of the chemical Flavin.
This molecule, which is an anthocyanin, is soluble in water and changes color in the presence of various types of solutions.

The pH paper is coated with this chemical, gives the property of changing colour at different pH solutions.

In the presence of an acidic solution, it turns red. In the presence of a basic solution, it turns greenish-Blue. In the presence of a neutral solution, it turns light green.