Simplify the pH Scale

If you want to understand Acidosis and Alkalosis, you’ve GOT to understand the pH scale.  It’s pretty easy to get confused by which direction is more acidic, and which direction is more basic.  And when you combine that with the anxiety you feel during an exam, you’re almost guaranteeing that you’ll end up second-guessing yourself…unless you have a no-fail way to understand the pH scale, and how it can be interpreted for acid and base imbalances.

ph Scale (0 = acidic, 7 = neutral, 14 = basic)

Start by making sure you’re familiar with the Ph Scale that you see pictured to the left.  Don’t waste time memorizing every example listed…just focus on the concept of pH.  After all, you probably already know that OJ is acidic, there’s really no reason you have to know that it has a pH of 3.  Save your brain space for something more important.

The pH scale can help you predict Acid-Base Imbalances

If a child arrives in the ER after a near-drowning in the ocean, then what is one (of many!) possible consequences that you should watch for as a nurse?  If you remember that Sea water is basic (pH 8 – although you don’t have to memorize that exact number), and you simultaneously realize that a near-drowning victim probably swallowed a lot of it, then you can conclude that there’s a chance that patient could develop Metabolic Alkalosis.  This is a perfect example of how you can use knowledge you already have, then use critical thinking to combine it and make an educated guess.  A very useful skill for NCLEX and HESI, and it’s essential for learning to think like a nurse.

But as I mentioned already, it can be a little tricky to keep the pH direction straight.  If acid increases, then pH decreases; but if base increases, then pH also increases.  How can you easily keep it straight?  Here’s two simple rules to help you can use:

  • If base increases OR acid decreases = pH increases
  • If base decreases OR acid increases = pH decreases

The pH moves in the opposite direction as acid (which happens to be H+, but more on that in a future article), while the pH moves in the same direction as base (which is usually bicarbonate).  As long as you remember those two simple rules for identifying the direction that pH needs to go, you’ll have a strong foundation for learning to interpret Arterial Blood Gases (ABGs).  And you’ll sweat a LOT less come test time.

Got a question about pH?  Leave a comment below to ask!

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  1. Josie

    I am studying for a test and this scenario has me confused.
    A depressed person attempts to commit suicide by taking a whole bottle of sleeping pills. The pills cause a drastic decrease in the pH and as a result the patient starts having breathing difficulties since thick and thin filaments with in the respiratory muscles are breaking down.

    Did this person’s pH become acidic or basic?

    What happens to the hydrogen concentration?

    • It usually helps me to write it down and draw arrows up or down to help me figure out which direction the pH is going. In this case, the scenario says that the pH decreases, which means it is becoming more acidic if you look at the pH scale. And to simplify, H+ (hydrogen) is what makes the body acidic. So whenever acidity increases, so does hydrogen concentration.

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