There are multiple definitions of acids and bases; we'll first introduce the Arrhenius definition. According to this definition, an acid produces hydrogen ions in solution, and a base produces hydroxide ions in solution. When an acid is in water, the hydrogen ion combines with water to produce the hydronium ion. H+ and hydronium are sometimes used interchangeably in aqueous solution. The formulas for acids are often written with the number of ionizable hydrogen atoms at the front of the formula. Some acids only have one ionizable hydrogen; they're called monoprotic acids. Although acetic acid has four hydrogen atoms, only one is ionizable, so the formula is written as HC2H3O2. Polyprotic acids have more than one ionizable hydrogen atom. For example, phosphoric acid has three ionizable hydrogen atoms, so it's called a triprotic acid, and its formula is H3PO4. A diprotic acid has two ionizable hydrogen atoms. Sulfuric acid is an example of a diprotic acid. All polyprotic acids ionize sequentially, so one hydrogen comes off first, then the other. The first hydrogen of sulfuric acid is a strong acid, so it completely ionizes in solution. We show the complete ionization of a strong acid using a single reaction arrow. Practically all of the H2SO4 molecules break apart to form hydrogen and hydrogen sulfate ions in solution. The second hydrogen of sulfuric acid is considered a weak acid, so it only ionizes to a relatively small extent. We show the partial ionization for weak acids using equilibrium arrows. Equilibrium arrows signify that both the forward and reverse reactions occur. This table contains common acids and bases. Six common strong acids to remember are hydrochloric acid, hydrobromic acid, hydroiodic acid, nitric acid, perchloric acid, and the first hydrogen atom of sulfuric acid. Common strong bases are hydroxide salts. Nitrogen bases like ammonia are weak bases. Although they do not contain hydroxide, they can react with water to remove an H+ ion, resulting in the production of hydroxide from water. Since they are weak bases, the reaction only occurs to a small extent. We have two types of acids we'll name: binary acids and oxyacids. Binary acids contain only hydrogen and a nonmetal. We name binary acids by adding a hydro prefix to the base name of the nonmetal, changing the ending of the nonmetal to -ic, and adding acid. For example, HCl is hydrochloric acid. Oxyacids contain an oxyanion. If the name of the oxyanion ends in -ate, we change the ending to -ic and add acid. We do not use the prefix hydro. If the name of the oxyanion ends with -ite, we change the ending to -ous and add acid; again, we do not use the prefix hydro. Let's practice naming acids. HBr is a binary acid, so we name it using the prefix hydro-, changing the ending of the nonmetal to -ic, and adding acid. HBr is hydrobromic acid. HBrO is an oxyacid. BrO- is hypobromite, so we change the -ite ending to -ous and add acid: HBrO is hypobromous acid. HBrO2 is also an oxyacid. It's formed from BrO2-, which is bromite, so we change the -ite ending to -ous and add acid: HBrO2 is bromous acid. Our last example, HBrO3, is also an oxyacid. It's formed from BrO3-, which is bromate. We change the -ate ending to -ic and add acid: HBrO3 is bromic acid. Next, let's talk about reactions. An Arrhenius acid and base can react to produce water and a salt. This type of reaction is also called a neutralization reaction. For example, hydrochloric acid reacts with sodium hydroxide to produce water and sodium chloride, which is a salt. We can also produce a weak electrolyte: for example, if we have a weak base like ammonia, we produce the ammonium ion. In an acid-base titration, we can use a neutralization reaction to determine an unknown concentration of an acid or base. In a titration, we have a solution of unknown concentration, which in this case is the acid. We also have a solution of known concentration, which in this case is the base. When the base is added to the acid, it neutralizes the acid, reducing the amount of H+ in solution. We can slowly add the base until we've completely reacted with the acid. The point at which we've added just enough base to completely react with the acid is called the equivalence point. We add an indicator to the acid solution to determine visually when we've reached this point. An indicator is a substance that is sensitive to the amount of H+ in solution and can change the color of the solution when a particular concentration of H+ is reached.