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The ocean contains a natural buffer system to maintain a pH between 8.1 and 8.3. [11] The oceans buffer system is known as the carbonate buffer system. [ 12 ] The carbonate buffer system is a series of reactions that uses carbonate as a buffer to convert C O 2 {\displaystyle \mathrm {CO_{2}} } into bicarbonate . [ 12 ]
[8] [9] [10] In modern chemistry, the p stands for "the negative decimal logarithm of", and is used in the term pK a for acid dissociation constants, [11] so pH is "the negative decimal logarithm of H + ion concentration", while pOH is "the negative decimal logarithm of OH − ion concentration".
At half-neutralization the ratio [A −] / [HA] = 1; since log(1) = 0, the pH at half-neutralization is numerically equal to pK a. 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.
Given its greater H + concentration, the formula yields a lower pH value for the weak base. However, pH of bases is usually calculated in terms of the OH − concentration. This is done because the H + concentration is not a part of the reaction, whereas the OH − concentration is. The pOH is defined as:
Assuming [4] that pH = −log 10 [H +] the pH can be calculated as pH = −log 10 x. If the degree of dissociation is quite small, C a ≫ x and the expression simplifies to = and pH = 1 / 2 (pK a − log C a).
The pH after the equivalence point depends on the concentration of the conjugate base of the weak acid and the strong base of the titrant. However, the base of the titrant is stronger than the conjugate base of the acid. Therefore, the pH in this region is controlled by the strong base. As such the pH can be found using the following: [1]
In a buffer, a weak acid and its conjugate base (in the form of a salt), or a weak base and its conjugate acid, are used in order to limit the pH change during a titration process. Buffers have both organic and non-organic chemical applications. For example, besides buffers being used in lab processes, human blood acts as a buffer to maintain pH.
Water molecules dissociate into equal amounts of H 3 O + and OH −, so their concentrations are almost exactly 1.00 × 10 −7 mol dm −3 at 25 °C and 0.1 MPa. A solution in which the H 3 O + and OH − concentrations equal each other is considered a neutral solution. In general, the pH of the neutral point is numerically equal to 1 / 2 ...