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Nitric acid is normally considered to be a strong acid at ambient temperatures. There is some disagreement over the value of the acid dissociation constant, though the pK a value is usually reported as less than −1. This means that the nitric acid in diluted solution is fully dissociated except in extremely acidic solutions.
The strength of a strong acid is limited ("leveled") by the basicity of the solvent. Similarly the strength of a strong base is leveled by the acidity of the solvent. When a strong acid is dissolved in water, it reacts with it to form hydronium ion (H 3 O +). [2] An example of this would be the following reaction, where "HA" is the strong acid:
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.
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 or base. When the pK a and analytical concentration of the acid are known, the extent of dissociation and pH of a solution ...
On the other hand, if a chemical is a weak acid its conjugate base will not necessarily be strong. Consider that ethanoate, the conjugate base of ethanoic acid, has a base splitting constant (Kb) of about 5.6 × 10 −10, making it a weak base. In order for a species to have a strong conjugate base it has to be a very weak acid, like water.
Acetic acid is an example of a weak acid. The pH of the neutralized solution resulting from HA + OH − → H 2 O + A −. is not close to 7, as with a strong acid, but depends on the acid dissociation constant, K a, of the acid. The pH at the end-point or equivalence point in a titration may be calculated as follows.
In dilute aqueous solution, the predominant acid species is the hydrated hydrogen ion H 3 O + (or more accurately [H(OH 2) n] +).In this case H 0 and H − are equivalent to pH values determined by the buffer equation or Henderson-Hasselbalch equation.
Commonly used mineral acids are sulfuric acid (H 2 SO 4), hydrochloric acid (HCl) and nitric acid (HNO 3); these are also known as bench acids. [1] Mineral acids range from superacids (such as perchloric acid) to very weak ones (such as boric acid). Mineral acids tend to be very soluble in water and insoluble in organic solvents.