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Nitric acid, with a pK value of around −1.7, behaves as a strong acid in aqueous solutions with a pH greater than 1. [23] At lower pH values it behaves as a weak acid. pK a values for strong acids have been estimated by theoretical means. [24] For example, the pK a value of aqueous HCl has been estimated as −9.3.
The higher the proton affinity, the stronger the base and the weaker the conjugate acid in the gas phase.The (reportedly) strongest known base is the ortho-diethynylbenzene dianion (E pa = 1843 kJ/mol), [3] followed by the methanide anion (E pa = 1743 kJ/mol) and the hydride ion (E pa = 1675 kJ/mol), [4] making methane the weakest proton acid [5] in the gas phase, followed by dihydrogen.
Note that the especially high molar values, as for paraffin, gasoline, water and ammonia, result from calculating specific heats in terms of moles of molecules. If specific heat is expressed per mole of atoms for these substances, none of the constant-volume values exceed, to any large extent, the theoretical Dulong–Petit limit of 25 J⋅mol ...
When using the ISO value of R, the calculated pressure increases by only 0.62 pascal at 11 kilometres (the equivalent of a difference of only 17.4 centimetres or 6.8 inches) and 0.292 Pa at 20 km (the equivalent of a difference of only 33.8 cm or 13.2 in).
NHCs are often strongly basic (the pKa value of the conjugate acid of an imidazol-2-ylidene was measured at ca. 24) [49] and react with oxygen. Clearly these reactions are performed using air-free techniques, avoiding compounds of even moderate acidity.
See Amino acid for the pK a values of all amino acid side chains inferred in such a way. There are also numerous experimental studies that have yielded such values, for example by use of NMR spectroscopy. The table below lists the model pK a values that are often used in a protein pK a calculation, and contains a third column based on protein ...
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Solid oxygen forms at normal atmospheric pressure at a temperature below 54.36 K (−218.79 °C, −361.82 °F). Solid oxygen O 2 , like liquid oxygen , is a clear substance with a light sky-blue color caused by absorption in the red part of the visible light spectrum.