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Bases with more than one OH- per formula unit are polyprotic. [16] The number of ionizable hydroxide (OH −) ions present in one formula unit of a base is also called the acidity of the base. [17] [18] On the basis of acidity bases can be classified into three types: monoacidic, diacidic and triacidic.
typical soft bases: organophosphines, thioethers, carbon monoxide, iodide; For example, an amine will displace phosphine from the adduct with the acid BF 3. In the same way, bases could be classified. For example, bases donating a lone pair from an oxygen atom are harder than bases donating through a nitrogen atom.
Alkalis are usually defined as a subset of the bases. One of two subsets is commonly chosen. A basic salt of an alkali metal or alkaline earth metal [2] (this includes Mg(OH) 2 (magnesium hydroxide) but excludes NH 3 ). Any base that is soluble in water and forms hydroxide ions [3] [4] or the solution of a base in water. [5]
An attempt to quantify the 'softness' of a base consists in determining the equilibrium constant for the following equilibrium: BH + CH 3 Hg + ⇌ H + + CH 3 HgB. 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 ...
Bases are defined by the Brønsted–Lowry theory as chemical substances that can accept a proton, i.e., a hydrogen ion. In water this is equivalent to a hydronium ion). The Lewis theory instead defines a Base as an electron-pair donor. The Lewis definition is broader — all Brønsted–Lowry bases are also Lewis bases.
The relative stability of the conjugate base of the acid determines its acidity. Other groups can also confer acidity, usually weakly: the thiol group –SH, the enol group, and the phenol group. In biological systems, organic compounds containing these groups are generally referred to as organic acids.
H 2 O is a base because it accepts a proton from CH 3 COOH and becomes its conjugate acid, the hydronium ion, (H 3 O +). [9] The reverse of an acid–base reaction is also an acid–base reaction, between the conjugate acid of the base in the first reaction and the conjugate base of the acid.
High equivalent weight (to minimize weighing errors) [3] Long lasting molar solution i.e. concentration remains unchanged for long periods of time; Non-toxicity; Ready and cheap availability (The last two are not as essential as the first four.) Some examples of primary standards for titration of solutions, based on their high purity, are ...