Pka Value
Pka Value - Related Videos
01:21
Factors Affecting Dissolution: Drug pKa, Lipophilicity and GI pH
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2024
Drug absorption within the gastrointestinal (GI) tract is a complex process influenced by several critical factors, including the site pH, the drug's dissociation constant (pKa), and the drug's lipophilicity. The GI tract exhibits a pH gradient, with an acidic environment in the stomach and a more alkaline environment in the small intestine. This pH variation directly affects the ionization state of drugs. A drug's pKa and the pH of the gastrointestinal (GI) tract play crucial roles in drug...
11:20
An Integrated System to Remotely Trigger Intracellular Signal Transduction by Upconversion Nanoparticle-mediated Kinase Photoactivation
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Cited by 1 •
2017
In this protocol, caged protein kinase A (PKA), a cellular signal transduction bioeffector, was immobilized on a nanoparticle surface, microinjected into the cytosol, and activated by the upconverted UV light from near-infrared (NIR) irradiation, inducing downstream stress fiber disintegration in the cytosol.
02:39
Indicators
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2020
Certain organic substances change color in dilute solution when the hydronium ion concentration reaches a particular value. For example, phenolphthalein is a colorless substance in any aqueous solution with a hydronium ion concentration greater than 5.0 × 10−9 M (pH < 8.3). In more basic solutions where the hydronium ion concentration is less than 5.0 × 10−9 M (pH > 8.3), it is red or pink. Substances such as phenolphthalein, which can be used to determine the pH of a solution, are called...
14:48
Acid and Base Concentrations - Student Protocol
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2020
Source: Smaa Koraym at Johns Hopkins University, MD, USA Preparation of ~0.1 M NaOHExpand In the first part of the lab, you will use a 50% w/w solution of NaOH to prepare 500 mL of ~0.1 M. The 50% w/w NaOH is indicative of its weight ratio. For example, if the instructor prepared 150 mL of the 50% w/w NaOH solution, then 150 g of NaOH was dissolved in 150 g of water, and the total weight of the solution is 300 g. To begin, put on the appropriate personal protective equipment,...
14:31
Buffers - Student Protocol
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2020
Source: Smaa Koraym at Johns Hopkins University, MD, USA Preparing 50 mM NaH2PO4 Buffer, pH 7Expand In the first part of this experiment, you will prepare a sodium phosphate solution buffered at pH 7.0. Monosodium phosphate is a weak acid with the conjugate base, disodium phosphate. Unadjusted monosodium phosphate solutions usually have a pH of about 4 - 6. Buffers are most effective close to their pKa, which is 6.8 to 7.2 for monosodium phosphate. So, you will use NaOH to push the...
FAQs
The numerical comparison is logarithmic: a one-unit difference in pKa represents a tenfold difference in Ka. Thus, the acid assigned the lower pKa has the larger dissociation constant and is expected to show greater proton dissociation at equilibrium. This makes pKa comparisons useful when ranking acids.
Protonation-state predictions require comparing the solution’s pH with the relevant acid’s pKa rather than considering the molecule in isolation. That comparison indicates which acid-base species is likely to dominate under the selected conditions. Consequently, pKa data help translate a molecular structure into an expected distribution of species for chemical analysis or reaction interpretation.
When two acid-base partners are compared, their pKa values provide a way to anticipate the favored direction of proton transfer. The comparison connects acid strength with the relative tendency of each partner to donate a proton at equilibrium. In chemistry, this helps explain why a proposed reaction may favor one set of acid-base species over another.
pKa values support interpretation in both aqueous and nonaqueous systems, but their meaning remains tied to the acid-base equilibrium being considered. Chemists use the value to connect proton donation with protonation state and molecular reactivity, then interpret those relationships within the solvent system relevant to the experiment. This supports comparisons across diverse chemical contexts.
Begin with the given Ka value and apply pKa = −log10(Ka). Because the conversion is logarithmic, the resulting number compresses large differences in dissociation constants into a convenient scale. Interpreting the calculated value then requires remembering its direction: smaller pKa values correspond to stronger acids and greater proton dissociation at equilibrium.
Buffer design uses pKa comparisons to identify an acid-base pair that represents the protonation conditions of interest. The value helps estimate which species will dominate at a selected pH, allowing the chemist to anticipate the balance between protonated and deprotonated forms. This makes pKa a central planning parameter for selecting a suitable buffer system.
Solubility assessment can use pKa to determine which protonation states are expected under a given pH. Because the dominant acid-base species depends on that state, pKa provides a chemical basis for interpreting how the solution environment may affect the species being assessed. This links acid-base behavior with practical evaluation of solubility.
In analytical chemistry, pKa values help identify the dominant acid-base species present at a selected pH, supporting interpretation of chemical measurements. In molecular reactivity studies, the same information connects protonation state with expected behavior. Together, these uses show why pKa is more than a strength ranking: it helps interpret chemical systems.