Now we can say that acids belong to a distinct class of covalent compounds because of their characteristics in aqueous solutions. Now here we can take a look at the solution, taste reactivity and how acid react with litmus paper when it comes to dissolution. We're going to say that they ionize into hydrogen or hydronium ions. Hydrogen ions are H+. Hydronium ions are H3O+. These two things are interchangeable. Later on when we go into further discussions of how acids react within aqueous environments, we'll see why that's true.
Now here we're going to say the ionize to hydrogen ion or hydronium ion, and an anion when dissolved in a solvent, typically water. So for example, here we have hydrochloric acid. When it dissolves into its ions, it gives us H+ (aq) + Cl- (aq), and then here we have sulfuric acid. If we were to just completely ionize it, where it gives off all of its H+ ions, we'd have 2 H+ (aq) + our sulfate ion (aq). Later on, we'll see that this doesn't really happen. When it when you your acid has multiple H+ ions, they actually are lost within steps. Right now we're not going into that detail. Just realize that if we were to just remove all the H in this particular example, we'd have 2 H+ at the end.
Now here for taste, we're going to say the presence of H+ or H3O+ ions give acids a sour taste. So if you want to think about sour, think of citrus fruit. We have lemons, we have oranges, they kind of have a sour taste to them. Now their reactivity we're going to say they react with metals to form H2 gas. A very common type of experiment that some of you may have done in lab is the reaction between hydrochloric acid and magnesium solid. Here, when we do this, we produce hydrogen gas plus magnesium chloride (aq). Here, let's not worry about balancing the equation. Just realize that we create these two things as products.
And finally, litmus paper. We're going to say litmus paper is a type of paper that changes colors and responds to an acid or a base for an acid. It changes red litmus paper or it changes blue litmus paper into red. So we take our blue litmus paper, dip it within an acidic solution, and when we pull it out, the blue litmus paper has changed to red. These are some of the most important characteristics of a typical acid.