pH

To maintain homeostasis, the human body employs many physiological adaptations. One of these is maintaining an acid-base balance. In the absence of pathological states, the pH of the human body ranges between 7.35 to 7.45, with the average at 7.40 (Hopkins et al., 2022).

The pH scale is a mathematical creation. It is a negative logarithm of the number of hydrogen ions (H⁺) in a solution, expressed as a number between 1 and 14, without units.

A logarithm is a way of restating an exponent. It's not the measurement itself, but the number of times you multiply to produce the actual number.
- Think of it like a ratio: The number of hydrogen ions per X number of dissolved molecules.
- The pH scale only reflects unmatched or net H⁺ions.

**The pH Scale**
1	7	14
The lower the pH, the more acid the substance.	Pure water has a neutral pH of 7	The higher the pH, the more alkaline the substance
An acid is a substance that, when dissolved in water, produces a net of hydrogen (H⁺) ions.		An alkali is a substance that, when dissolved in water, yields a net of hydroxide (OH^-) ions.

Instant Feedback:

Low pH is:

If you have oneH⁺and one OH^-together, you have water.

(H⁺) + (OH^-) = H2O

What's the significance of the OH^- ion?
- From the above equation you can see that OH^- would neutralize H⁺ if it were available.
- You might think of OH^- as "negative hydrogen", or "anti-hydrogen."
- If you have one H⁺and an OH^-is available, the H⁺would be neutralized.
  - You will not increase the free H⁺until you use up the OH^-.
- There is such a thing as pOH, (though for practical purposes, we never use it.)
  - H⁺ is now "anti OH^- " and neutral is still neutral.
  - H⁺and OH^- are such perfect opposites that they're "almost the same."

Points to remember:

The pH scale goes from 1 to 14.
Low pH is acid.
High pH is alkaline.
pH 7 is Neutral

Visit pH Playground from the Acid-Base Tutorial website by Alan Grogono
Click on "Understand pH"