How to identify Acids & Bases

An acid (for example, hydrochloric acid, HCl) is a substance that releases or donates the hydrogen ion (H+), while a base (for example, sodium hydroxide, NaOH) is a hydrogen ion acceptor. The pH scale, which ranges from 0 to 14, determines how basic or acidic a solution is. Acids usually have pH below 3. A strongly base solution is above 10 on the pH scale. A neutral level--water, for example--registers 7 on the pH scale.

Things You'll Need

• Hydrion pH paper
• Beaker, 10 ml

Instructions

1. Purchase wide range pH paper. See the Resources section for a source.

2. Add 2 to 5 ml of the sample solution into the beaker.

3. Cut a piece (about 1.5 inches long) of the pH paper.

4. Put the end pH paper strip into the water sample for one to two seconds, and then take it out. The part of the paper that has been in the water will change color.

5. Compare the paper color with the scale printed on the pack of the hydrion pH paper. Typically, if the color is red or orange the sample is an acid. If the color is blue or dark blue, the substance is a base.

References

• "Introduction to acid-base chemistry", Stephen K. Lower

Resources

• Wide Range pH Paper