Explore this lesson to learn about conjugate acids, how they are different from other acids, and where to find them in a given acid-base equation.
Then, apply what you have learned, in this lesson, to examples involving conjugate acids.
History of Acids
Did you know conjugate acids belong to the larger family of acids? As a member of this family they have taken on similar traits as the other acids, but, of course, have their own distinct traits that make them unique within the family. Before we jump into learning about what makes a conjugate acid different from its acidic family members, let’s learn more about conjugate acid’s historical lineage.An acid is a type of solution that can be found widely throughout our environment. This may seem like a very broad definition of an acid, but there is a great reason for this broad definition.
Technically, an acid has three different definitions, all created by theories. An acid can be labeled as an Arrhenius acid, which has an ability to break apart in solution to create hydrogen ions. An acid can also be labeled as a Bronsted-Lowry acid, which has the ability to donate protons in solution. An acid can be a Lewis acid, which can accept electron pairs in solution. Each of these labels build the family tree of acids.Now, you may know that acids can also be strong or weak.
This is most certainly true! Depending on its strength in solution, or should we say how many muscles an acid can flex, an acid can be strong or weak. So where do conjugate acids fit into this discussion? So glad you asked! Let’s look at what conjugate acids are and why they belong to this family of acids.
Definition ; Formation
Conjugate acids are a type of acid that gains a proton in solution. These acids will gain a proton in response to a base that has happily accepted a proton. This fits perfectly into the family lineage of acids because conjugate acids describe what a Bronsted-Lowry acid is.Something to keep in mind with conjugate acids is that they just don’t randomly pop up and say hello in a solution. Rather, they are created from an acid-base process involving the acceptance or donation of protons.
Specifically, a conjugate acid is created from a base. I know you may be thinking, ‘Wait a minute… a base? What does that have to do with acids?’ Well when a lonely base ion interacts with water, something happens to that base ion. It happily gains a proton.
As a result, this newly formed molecule is no longer called a base but a conjugate acid.Again, this supports the idea that conjugate acids are not free floating around everywhere. They are created through this process, specifically when a base, strong or weak, is present in solution.
Let’s practice how to spot a conjugate acid in acid-base equations by looking at a few examples.
Examples of Conjugate Acids
Nitric Acid in Water: Nitric acid is a strong acid that is commonly used in industrial settings to make fertilizers. When it reacts with water (a base), one of the products formed is a conjugate acid. Can you identify the conjugate acid? The conjugate acid is the hydronium ion, or H3O+, as the base. H2O accepted a proton from the nitric acid to form H3O+.
This newly formed product gained a proton to become H3O+. See, that wasn’t too painful, was it? Let’s look at another example.Hydrogen Sulfate and Ammonia: In this example, hydrogen sulfate (HSO4-) is a strong acid reacting with our friend, the weak base ammonia (NH3). When these two molecules interact one of the products formed is a conjugate acid. Can you guess what the conjugate acid is? Bingo! The conjugate acid is the ammonium ion. This is because ammonia graciously accepted a proton from hydrogen sulfate, resulting in the formation of the ammonium ion. A proton was gained in order to form this conjugate acid.
Conjugate acids are a type of acid that is formed when a base accepts a proton in solution. These acids can also be defined as gaining a proton in solution. As an acid, it falls under the category of Bronsted-Lowry acids/bases, which has the ability to donate protons in solution.
Conjugate acids are not free floating in solution, but rather are a product of Bronsted-Lowry acid-base reactions. A conjugate acid is the product that is different from a base by one proton. Examples of conjugate acids include water (base) reacting with an acid to form the hydronium ion (conjugate acid), and ammonia (base) reacting with an acid to form the ammonium ion (conjugate acid).