Acid-Base Balance: Videos & Practice Problems

Acids and Bases

In this video, we're going to begin our lesson on acids and bases. And so what you all need to know is that many biological processes are actually strongly affected by the concentration of dissolved hydrogen ions or H⁺ ions in the aqueous solution. And so the concentration of dissolved hydrogen ions can really just be abbreviated by brackets with an H⁺ in the middle. And so anytime you see brackets in science, it means the concentration of. And so what this brackets means is the concentration of hydrogen ions.

And so acids and bases are substances that directly affect the concentration of hydrogen ions. And once again, the concentration of hydrogen ions is really, really important because that will strongly affect many biological processes that we'll talk about later in our course. But in our next lesson video, we're going to talk in more details about exactly how acids directly affect the hydrogen ion concentration. And then later in a different video, we'll talk about how bases directly affect the hydrogen ion concentration. And so I'll see you all in our next lesson video to talk about acids.

Acids

In this video, we're going to introduce acids. Acids are essentially any chemical that increases a solution's concentration of hydrogen ions, or H⁺ ions. Once again, recall that the concentration of hydrogen ions can be abbreviated with brackets like this, [H⁺], because anytime we see the brackets in science, we know it means the concentration of what's in between the brackets. So, this is the concentration of hydrogen ions here.

Acids will increase the concentration of hydrogen ions in solution. If we take a look at our example below at the addition of hydrochloric acid or HCl to water, we can see an example of an acid. Notice over here on the far left, we're showing you four different molecules of hydrochloric acid, or HCl, one, two, three, and four. As its name implies, hydrochloric acid is an acid, which means that when we add it to water, it is going to increase the concentration of hydrogen ions. What happens when we add a hydrochloric acid molecule to water, it will actually split up into two components.

It will split up into a hydrogen ion, H⁺, and a chloride anion, Cl^-. Each HCl molecule splits into H⁺ and Cl^- when added to pure water. Notice over here in this beaker, we have these chloride anions here, three of four of them for that matter since we have four HCl molecules, and we also have four hydrogen ions. Ultimately, what we can see is that through the addition of HCl to pure water, at the end, we have an increase in the concentration of hydrogen ions. We have more hydrogen ions in the solution than what we had before.

We can say that we have increased the hydrogen ion concentration. And really, that is it for acids. Acids are any substance that will increase the concentration of hydrogen ion. The concentration of hydrogen ion is very important when it comes to biological processes. We'll get to learn more about that as we move forward in our course.

But in our next video, we're going to talk about bases. So I'll see you all there.

Bases

So now that we've introduced acids in our previous lesson videos, in this video we're going to introduce bases. Bases are practically the opposite of acids because instead of increasing a solution's hydrogen ion concentration, bases are any chemical that decreases a solution's hydrogen ion concentration or concentration of hydrogen ions. An example of a base is sodium hydroxide whose chemical formula is NaOH. If we take a look at our example image down below, we'll be able to see an example of a base, specifically the addition of sodium hydroxide to water. Notice on the left-hand side over here, what we're showing you are three different sodium hydroxide molecules.

One, two, and three. When each of these sodium hydroxide molecules is added to water, the sodium hydroxide dissociates or breaks apart into ions. For example, this sodium hydroxide molecule will break apart into a sodium ion (Na⁺) and a hydroxide ion (OH^-). This is true for each of these sodium hydroxide ions, and notice upon the addition of the sodium hydroxide to the pure water, the ions break apart. So, you'll see three hydroxide ions and three sodium ions.

Now you'll notice that even in pure water over here, we're showing you some hydrogen ions, and this is true even for pure water, as there will be some hydrogen ions. This is because water has the ability to auto-ionize, which is something that we'll talk more about later in our course. But for now, notice that there are some hydrogen ions even in pure water, and so you can see those hydrogen ions over here as well. What's important to note is that each of these hydroxide ions will interact with a hydrogen ion, and when the hydroxide ion interacts with the hydrogen ion, they create water molecules as you see right here. As a result, the concentration of hydrogen ions is decreased because of the addition of the sodium hydroxide.

Whereas there were three hydrogen ions in the pure water and this beaker here, in the final beaker, notice that there are not any hydrogen ions being shown. This shows the decreased hydrogen ion concentration. Once again, when a chemical decreases a solution's concentration of hydrogen ions, that chemical is referred to as a base. Sodium hydroxide is indeed a base. Once again, the concentration of hydrogen ions is incredibly relevant to living systems, and any substance that can change a concentration of hydrogen ions is going to be relevant as well, so bases are very important. This here concludes our brief introduction to bases, and we'll be able to get some practice applying these concepts as we move forward.

So, I'll see you all in our next video.