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The pH range is commonly given ... = √ K w, or pH = pK w /2. pK w is approximately 14 but depends ... typically have a pH below 4.6 [34] with sharp and tangy taste ...
If pH is below the pK a or pK b value, the converse is true. Usually, the color change is not instantaneous at the pK a or pK b value, but a pH range exists where a mixture of colors is present. This pH range varies between indicators, but as a rule of thumb, it falls between the pK a or pK b value plus or minus one. This assumes that solutions ...
Conversely, when pH = pK a, the concentration of HA is equal to the concentration of A −. The buffer region extends over the approximate range pK a ± 2. Buffering is weak outside the range pK a ± 1. At pH ≤ pK a − 2 the substance is said to be fully protonated and at pH ≥ pK a + 2 it is fully dissociated (deprotonated).
It follows that the range of pH within which there is partial dissociation of the acid is about pK a ± 2. This is shown graphically at the right. This is shown graphically at the right. A practical application of these results is that the pH transition range of a pH indicator is approximately p K a ± 1; the colour of the indicator in its acid ...
With pOH obtained from the pOH formula given above, the pH of the base can then be calculated from =, where pK w = 14.00. A weak base persists in chemical equilibrium in much the same way as a weak acid does, with a base dissociation constant (K b) indicating the strength of the base. For example, when ammonia is put in water, the following ...
Buffer capacity falls to 33% of the maximum value at pH = pK a ± 1, to 10% at pH = pK a ± 1.5 and to 1% at pH = pK a ± 2. For this reason the most useful range is approximately pK a ± 1. When choosing a buffer for use at a specific pH, it should have a pK a value as close as possible to that pH. [2]
Universal buffers consist of mixtures of acids of diminishing strength (increasing pK a), so that the change in pH is approximately proportional to the amount of alkali added. It consists of a mixture of 0.04 M boric acid, 0.04 M phosphoric acid and 0.04 M acetic acid that has been titrated to the desired pH with 0.2 M sodium hydroxide. Britton ...
The Henderson-Hasselbalch equation can be used to model these equilibria. It is important to maintain this pH of 7.4 to ensure enzymes are able to work optimally. [12] Life threatening Acidosis (a low blood pH resulting in nausea, headaches, and even coma, and convulsions) is due to a lack of functioning of enzymes at a low pH. [13]