Stabilization of a conjugate base: resonance. Stabilization of a conjugate base: induction. Stabilization of a conjugate base: hybridization. Stabilization of a conjugate base: solvation. Anne Marie Helmenstine, Ph. Chemistry Expert. Helmenstine holds a Ph. She has taught science courses at the high school, college, and graduate levels.
Facebook Facebook Twitter Twitter. Updated November 11, A lower pKa value indicates a stronger acid. That is, the lower value indicates the acid more fully dissociates in water. Featured Video. Cite this Article Format. Helmenstine, Anne Marie, Ph. List of the Strong Acids and Key Facts. It is a variation on that line from the Wizard of Oz, "We don't live in water anymore. It is a very good idea to commit to memory the approximate pK a ranges of the compounds above.
If you are asked to say something about the basicity of ammonia NH 3 compared to that of ethoxide ion CH 3 CH 2 O - , for example, the relevant pK a values to consider are 9. From these numbers, you know that ethoxide is the stronger base. Do not make the mistake of using the pK a value of this is the pK a of ammonia acting as an acid , and tells you how basic the NH 2 - ion is very basic!
Biochemistry and organic chemistry texts often list the value as These texts have incorrectly factored the molar value for the concentration of water into the equilibrium constant. The correct derivation of the equilibrium constant involves the activity of water, which has a value of 1. HA may or may not be soluble, so it may or may not precipitate. The higher the pKa, the lower the Ka, the lower the ratio of A- to HA, and thus the higher fraction of molecules of substance A will be in the non dissociated state.
I think users jerepierre and t. First we need to understand what happens with an acid with a specified pKa value , when a solution reaches certain pH values. Without knowing more about the specific chemical nature of the molecule, we cannot know more about what will happen.
In general, in a water solution more deprotonated or protonated acids will be more soluable more molecules stays in solution. This is a result of that part of the molecule gaining an electric charge when gaining or losing extra protons. This charge makes the molecule polar, and soluable in polar solutions such as water. Solubility of a molecule can be explained using another concept that relates to pKa. This is called the isoelectric point pI. Sometimes molecules are large, and complex.
Several different parts of such a large molecule can be either 'acidic' or 'basic', depending on their chemical nature. They then gain or lose charge differently as the pH of a solution changes. At a certain pH, all the charges even out and the molecule becomes neutrally charged instead of positive, or negative. It then loses its polarity which makes it soluable in water and it precipitates. By specifying that A is lidocaine I could say that by adding HCl to it you'd be forming a diferent compound, lidocaine hydrocloride.
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