Buffer capacity
In chemistry , the buffer capacity , also called buffering capacity , describes the amount of acid or base that can be absorbed by a buffer without a significant change in the pH value . It is therefore a measure of the stability of the pH value of a solution when strong bases or strong acids are added.
The buffer capacity indicates how many oxonium ions (H 3 O + ) or hydroxide ions (OH - ) can be added to a certain volume of a solution until its pH value has reached a certain value or until its pH value is around a unit is lowered or raised. The unit of buffer capacity is millimoles per liter or moles per cubic meter.
The buffer capacity depends on the concentrations of weak acids and bases in the solution that make up the buffer . In a solution, H 3 O + can only be buffered if the weak base is still present in sufficient concentrations. Similarly, OH - can only be buffered if there is still enough weak acid. The higher the concentrations of the weak acid and base in a solution, the greater the buffer capacity. This is greatest when buffer acid and salt are present in equimolar amounts. As a rule of thumb, one can say that a buffer is exhausted as soon as the ratio of the acid / base concentration exceeds the value 1 to 10 (or 10 to 1). The pH of a buffer can therefore fluctuate ± 1 before it is exhausted.
In human blood , the so-called alkali reserve (a supply of alkaline buffering substances) ensures a buffer capacity in relation to the solution of carbon dioxide (“ blood buffer ”).
See also
Individual evidence
- ↑ a b c d e Müfit Bahadır , Harun Parlar , Michael Spiteller (eds.): Springer-Umweltlexikon. Springer Verlag, Berlin / Heidelberg / New York, 1995. ISBN 3-540-54003-2 , p. 828.
- ↑ a b DIN 38409-7: 2005-12 German standard methods for the examination of water, waste water and sludge - summary action and substance parameters (group H) - part 7: determination of acid and base capacity (H 7). Beuth Verlag, Berlin. P. 8.