Now we're going to say, a species with a pH greater than 7 is classified as basic. If you're basic, you're going to say that your H+ concentration is less than your OH- concentration. And we can also say that the stronger the base, then the higher the pH. And the higher the pH, the greater your hydroxide concentration. We can understand this relationship as the strongest base would have the highest pH. And therefore, have the highest OH- concentration. And remember, we already went over this several videos ago. How do we determine if something is weak or strong? You still need to know those in order to do the following questions. Because again, I've said it so many times before. Why do we need to know the strength of things? Because eventually, we're going to have to use ice charts to find pH if we're given a weak acid or a weak base. That's why it's important to know what our species is. Is it weak or is it strong?
Now, we're going to say a species with a pH less than 7 is termed acidic. And if you're acidic, your H+ concentration is greater than your OH- concentration. Here we can say the stronger the acid, then the lower the pH. The strongest acid has the lowest pH, which means you have the highest H+.
And finally, we're going to say a species with a pH equal to 7 is neutral. Remember, this is only true at 25 degrees Celsius because remember, at 25 degrees Celsius, Kw equals 1.0×10-14. If they were to change the temperature, that would change our Kw, and then neutral pH would become a new number. It doesn't always equal 7. And we're going to say here, if you're neutral, then your H+ concentration is equal to your OH- concentration.