A byproduct of the pickling process changes the flavor of the vegetables with the acid making them taste sour. For example, drugs often need to be water soluble for maximum effectiveness. However, many complex organic compounds are not soluble or are only slightly soluble in water. Fortunately, those drugs that contain proton-accepting nitrogen atoms and there are a lot of them can be reacted with dilute hydrochloric acid [HCl aq ].
The modified drug molecules can then be isolated as chloride salts:. Drugs that are modified in this way are called hydrochloride salts. Examples include the powerful painkiller codeine, which is commonly administered as codeine hydrochloride. Acids other than hydrochloric acid are also used. Hydrobromic acid, for example, gives hydrobromide salts. Dextromethorphan, an ingredient in many cough medicines, is dispensed as dextromethorphan hydrobromide.
The accompanying figure shows another medication lidocaine as a hydrochloride salt. According to the Bronsted-Lowry theory of acids and bases, an acid is a proton donor and a base is a proton acceptor. Once an acid has given up a proton, the part that remains is called the acid's conjugate base.
This species is a base because it can accept a proton to re-form the acid. The conjugate base of HF first example below is fluoride ion, F -. Similarly, the part of the base that remains after a base accepts a proton is called the base's conjugate acid. This species is an acid because it can give up a proton and thus re-form the base.
The conjugate acid of fluoride ion, F - first example below is HF. The table below lists conjugate acid-base pairs for your reference so that you can figure out the strategy of identifying them. For any given acid or base, you should be able to give its conjugate base or conjugate acid. In the reaction of ammonia with water to give ammonium ions and hydroxide ions, ammonia acts as a base by accepting a proton from a water molecule, which in this case means that water is acting as an acid.
The sulfate ion is the conjugate base of the hydrogen sulfate ion. In the reaction illustrated below, water serves both as acid and base simultaneously. One water molecule serves as an acid and donates a proton.
The other water molecule functions as a base by accepting the proton. Skip to main content. Acids and Bases. Search for:. Define amphoterism.
Define conjugate acid. Define conjugate base. Write reactions that illustrate the idea of conjugate acid-base pairs. A new theory The Arrhenius concept of acids and bases was a significant contribution to our understanding of acids and bases.
Figure 1. Lone pair electrons on nitrogen. Which direction? Figure 2. Water molecules as a conjugate acid-base pair. Summary Conjugate acids and bases are defined. Examples of conjugate acid-base pairs are given. Why is the chloride anion considered a base? Review In the reaction between ammonia and water, how does the ammonia serve as a base on the left-hand side of the equation?
If the reaction is viewed in reverse a new acid and base can be identified. The substances on the right side of the equation are called conjugate acid and conjugate base compared to those on the left. Also note that the original acid turns in the conjugate base after the reaction is over.
For a reaction to be in equilibrium a transfer of electrons needs to occur. The acid will give an electron away and the base will receive the electron. Acids and Bases that work together in this fashion are called a conjugate pair made up of conjugate acids and conjugate bases.
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