How do you do an experiment to find whether a liquid is acidic or alkaline?

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gsenviro | College Teacher | (Level 1) Educator Emeritus

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There are a number of way in which one can determine whether a liquid is an acid or a base. The laboratory method would be to simply measure its pH, a value above 7 indicates a base and value less than 7 confirms an acid.

At school level, esp. during an introductory chemistry course, we can use either litmus paper or red cabbage juice. The acid/base determination is based on the color. Here are the steps for litmus paper based test:

1) Pour the liquid to be tested in a small bowl or glass.

2) Dip a piece of red litmus paper in it and note the color change. Repeat the process with a piece of blue litmus paper.

If, the red litmus turns blue and blue litmus remains unchanged, liquid is a base. 

If, the blue litmus turns red and red litmus stays unchanged, liquid is an acid. 

If, neither the red nor the blue litmus paper changes color, it is a neutral liquid.

Red cabbage juice can also be used and students can add few drops of the liquid in a tablespoon full of red cabbage juice and observe its color. If the juice turns red, liquid is an acid; if juice turns blue (or green), liquid is a base.

Hope this helps.

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