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Any acid with a value which is less than about -2 behaves as a strong acid. This results from the very high buffer capacity of solutions with a pH value of 1 or less and is known as the leveling effect. [3] The following are strong acids in aqueous and dimethyl sulfoxide solution.
An organic acid is an organic compound with acidic properties. The most common organic acids are the carboxylic acids, whose acidity is associated with their carboxyl group –COOH. Sulfonic acids, containing the group –SO 2 OH, are relatively stronger acids. Alcohols, with –OH, can act as acids but they are usually very weak.
Electron-withdrawing substituents, such as -CF 3 group, give stronger acids (the pK a of acetic acid is 4.76 whereas trifluoroacetic acid, with a trifluoromethyl substituent, has a pK a of 0.23). Electron-donating substituents give weaker acids (the p K a of formic acid is 3.75 whereas acetic acid, with a methyl substituent , has a p K a of 4.76)
A strong acid, such as hydrochloric acid, at concentration 1 mol dm −3 has a pH of 0, while a strong alkali like sodium hydroxide, at the same concentration, has a pH of 14. Since pH is a logarithmic scale, a difference of one in pH is equivalent to a tenfold difference in hydrogen ion concentration.
Stepwise dissociation constants are each defined for the loss of a single proton. The constant for dissociation of the first proton may be denoted as K a1 and the constants for dissociation of successive protons as K a2, etc. Phosphoric acid, H 3 PO 4, is an example of a polyprotic acid as it can lose three protons.
Other acidity functions have been proposed for different environments, most notably the Hammett acidity function, H 0, [3] for superacid media and its modified version H − for superbasic media. The term acidity function is also used for measurements made on basic systems, and the term basicity function is uncommon.
where CH 3 Hg + (methylmercury ion) is a very soft acid and H + (proton) is a hard acid, which compete for B (the base to be classified). Some examples illustrating the effectiveness of the theory: Bulk metals are soft acids and are poisoned by soft bases such as phosphines and sulfides.
Nitric acid is an inorganic compound with the formula H N O 3.It is a highly corrosive mineral acid. [6] The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into oxides of nitrogen.