pH

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.
 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:
Acidosis
Alkalosis

If you have one H+ 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 there is an OH- 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:

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

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