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For example the value of log K ≈ −6 has been estimated for hydrogen chloride in aqueous solution at room temperature. [1] A chemical compound may behave as a strong acid in solution when its concentration is low and as a weak acid when its concentration is very high. Sulfuric acid is an example of such a compound.
Acetic acid is a weak acid, so it only ionizes slightly. According to Le Chatelier's principle, the addition of acetate ions from sodium acetate will suppress the ionization of acetic acid and shift its equilibrium to the left. Thus the percent dissociation of the acetic acid will decrease, and the pH of the solution will increase.
For example, acetic acid is a weak acid which has a = 1.75 x 10 −5. Its conjugate base is the acetate ion with K b = 10 −14 /K a = 5.7 x 10 −10 (from the relationship K a × K b = 10 −14), which certainly does not correspond to a strong base. The conjugate of a weak acid is often a weak base and vice versa.
In water, measurable pK a values range from about −2 for a strong acid to about 12 for a very weak acid (or strong base). A buffer solution of a desired pH can be prepared as a mixture of a weak acid and its conjugate base. In practice, the mixture can be created by dissolving the acid in water, and adding the requisite amount of strong acid ...
Simply because a substance does not readily dissolve does not make it a weak electrolyte. Acetic acid (CH 3 COOH) and ammonium (NH + 4) are good examples. Acetic acid is extremely soluble in water, but most of the compound dissolves into molecules, rendering it a weak electrolyte. Weak bases and weak acids are generally weak electrolytes.
Although hydrofluoric acid is regarded as a weak acid, it is very corrosive, even attacking glass when hydrated. [ 20 ] Dilute solutions are weakly acidic with an acid ionization constant K a = 6.6 × 10 −4 (or p K a = 3.18 ), [ 10 ] in contrast to corresponding solutions of the other hydrogen halides, which are strong acids ( p K a < 0 ).
If it is the result of a reaction between a strong base and a weak acid, the result is a base salt. If it is the result of a reaction between a strong acid and a strong base, the result is a neutral salt. Weak acids reacted with weak bases can produce ionic compounds with both the conjugate base ion and conjugate acid ion, such as ammonium acetate.
What makes these compounds basic is that the conjugate base from the weak acid hydrolyzes to form a basic solution. In sodium carbonate, for example, the carbonate from the carbonic acid hydrolyzes to form a basic solution. The chloride from the hydrochloric acid in sodium chloride does not hydrolyze, though, so sodium chloride is not basic.