The pH Scale of Common Chemicals

The pH scale shows how acidic or basic a chemical is in aqueous solution (mixed with water). The scale runs from 0 (most acidic) to 14 (most alkaline or basic), where 7 is neutral pH. Chemicals with pH values from 0 up to 7 are acids, those with a pH value of 7 are neutral, and those with pH values greater than 7 up to 14 are bases. Here is a table of pH values of common chemicals.

Key Takeaways: pH Scale of Common Chemicals

• The pH scale measures how acidic, neutral, or basic a substance is in water, ranging from 0 (strong acid) to 14 (strong base), with 7 as neutral.
• Acids have pH < 7, bases (alkaline) have pH > 7, and pure water is neutral at pH 7.
• Many common foods, household products, and body fluids have characteristic pH values.
• pH affects biological processes, chemical reactions, cleaning effectiveness, and environmental health.
• You can measure pH using meters, indicators, or test strips, with more precise methods available in laboratories.

pH Values of Common Chemicals

You’ll see charts that give slightly different pH values for some chemicals. There’s usually a pH range for a substance. For example, fruit acidity depends on soil, temperature, ripeness, and other factors. The pH of a soap depends on other ingredients in its formula. Soil pH ranges anywhere from 3 to 10. So, don’t get too caught up in the numbers.

Common Acids

Acids include chemicals with the word “acid” in their name. Examples include hydrochloric acid, acetic acid, and hyaluronic acid. Most fruits and vegetables are acidic. So is human skin and hair, which has a low pH to help protect the body from pathogens. Coffee, tea, wine, and milk are all acidic. Stomach acid is, of course, acidic.

Neutral Chemicals

Pure water is neutral. However, tap water may be slightly acidic or basic. Dissolving table salt in water does not change its pH, so ordinary salt water is neutral. Sea water is alkaline and not neutral. Fresh milk is nearly neutral, but it becomes more acidic as it sours. Vegetable oil is not an aqueous solution, so pH testing with water-based methods is not meaningful for it.

Common Bases

Common bases include baking soda (sodium bicarbonate), washing soda (sodium carbonate), and household cleaning products like bleach, ammonia, and drain cleaner. Human blood is slightly basic, as are eggs and seawater.

What Is pH?

The numbers of the pH scale come from a formula for the hydrogen ion (H⁺) concentration. The pH scale is logarithmic, meaning each whole number change represents a tenfold change in hydrogen ion concentration. Acids donate hydrogen ions (protons), while bases accept them or release hydroxide ions. The equation for pH is:

pH = -log[H⁺]

Similarly, pOH is a measure of the hydroxide ion (OH^–) concentration. Because bases don’t have free hydrogen ions, it’s sometimes easier to calculate pOH.

pOH = -log[OH^–]

pH and pOH are related. At room temperature:

pH + pOH = 14

How to Measure pH

There are several ways to measure pH.

• In a lab, you use a pH meter for the most sensitive readings. However, pH meters are expensive and require calibration.
• Universal indicator is a liquid mixture displays a rainbow of colors. Adding a drop of a sample to a spot of universal indicator turns it a color that corresponds to a pH range. Other indicators are used for more accurate readings within narrow pH ranges.
• For home or school, pH paper test strips are a good option. Litmus paper turns red, purple, or blue to roughly estimate pH values. You’d don’t have to buy litmus paper, though. It’s easy to make homemade pH paper test strips using cabbage juice or another natural pH indicator.

Why pH Matters

The pH of a chemical solution affects how it interacts with materials, living organisms, and the environment. Many biological processes, like enzyme activity and blood chemistry, only work properly within a narrow pH range. For example, human blood must stay around pH 7.4. If it drops or rises too much, serious health problems occur.

In everyday life, pH helps you choose safe and effective products. Acidic solutions can corrode metals and irritate skin, while strong bases can damage hair, skin, and eyes. In agriculture and gardening, soil pH determines what plants will thrive. Environmental scientists monitor pH to track acid rain and water pollution, because aquatic life depends on balanced pH levels.

Understanding pH helps you handle chemicals safely, protect the environment, and maintain health.

FAQ About the pH Scale

What does pH stand for?
pH stands for “potential of hydrogen” or “power of hydrogen,” referring to the concentration of hydrogen ions (H⁺) in a solution.

Can pH be lower than 0 or higher than 14?
Yes. While the scale is often shown as 0–14, concentrated acids can have pH values below 0, and concentrated bases can have pH values above 14.

Is neutral pH always 7?
Only at 25 °C (77 °F) in pure water. The neutral point shifts slightly with temperature because the water ionization constant changes.

Why is pH important for skin and hair?
Healthy skin and hair are slightly acidic, which helps prevent infections and keeps the cuticle layer of hair smooth. Using products with the wrong pH can cause dryness, irritation, or damage.

How does pH affect the environment?
Acid rain and acidified oceans harm plants, fish, and other wildlife. Monitoring and managing pH helps protect ecosystems.

References

• Myers, Rollie J. (2010). “One-Hundred Years of pH”. Journal of Chemical Education. 87 (1): 30–32. doi:10.1021/ed800002c
• Slessarev, E. W.; Lin, Y.; Bingham, N. L.; Johnson, J. E.; Dai, Y.; Schimel, J. P.; Chadwick, O. A. (November 2016). “Water balance creates a threshold in soil pH at the global scale”. Nature. 540 (7634): 567–569. doi:10.1038/nature20139
• Tarun, J.; Susan, J.; Suria, J; Susan, V.J.; Criton, S. (2014). “Evaluation of pH of Bathing Soaps and Shampoos for Skin and Hair Care.” Indian J Dermatol. 59 (5): 442-4. doi:10.4103/0019-5154.139861