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Principle of buffer solution and pH value
When a certain amount of acid and alkali is added to some solutions, it has the effect of hindering the pH change of the solution, which is called buffering. Such solutions are called buffering solutions. The mixed solution of weak acid and its salt (such as HAc and NaAc), the mixed solution of weak base and its salt (such as NH3·H2O and NH4Cl) are all buffer solutions.
The buffer solution composed of the weak acid HA and its salt NaA buffers the acid due to the presence of sufficient alkali A- in the solution. When a certain amount of strong acid is added to this solution, H ions are basically consumed by A-ions:
so the pH value of the solution is almost unchanged; when a certain amount of strong alkali is added, the weak acid HA in the solution consumes OH- ions And hinder the change of pH.
Many important reactions in chemistry and biochemistry are pH-dependent, meaning that the pH of the solution can play an important role in determining whether and how rapidly a reaction takes place. Consequently, buffers—solutions that help keep the pH stable– -are important for running many experiments. Sodium acetate is a weakly basic salt and the conjugate base of acetic acid, or vinegar. A mixture of sodium acetate and acetic acid makes a good buffer for weakly acidic solutions. A few different ways exist to prepare an acetate buffer, but one method in particular is straightforward and relatively safe.