A buffer is a special solution that stops massive changes in pH levels. Every buffer that is made has a certain buffer capacity, and buffer range. The buffer capacity is the amount of acid or base that can be added before the pH begins to change significantly. It can be also defined as the quantity of strong acid or base that must be added to change the pH of one liter of solution by one pH unit. The buffer range is the pH range where a buffer effectively neutralizes added acids and bases, while maintaining a relatively constant PH.
To effectively maintain a pH range, a buffer must consist of a weak conjugate acid-base pair, meaning either a. A weak acid and its conjugate base, or b. A weak base and its conjugate acid. The use of one or the other will simply depend upon the desired pH when preparing the buffer. A buffer is able to resist pH change because the two components (conjugate acid and conjugate base) are both present in appreciable amounts at equilibrium and are able to neutralize small amounts of other acids and bases (in the form f HUH+ and OH-) when they are added to the solution.
Buffers function best when the peak of the conjugate weak acid used is close to the desired working range of the buffer. This turns out to be the case when the concentrations of the conjugate acid and conjugate base are approximately equal (within about a factor of 10). Over the working range of the buffer, pH changes very little with the addition of acid or base. Once the buffering capacity is exceeded the rate of pH change quickly jumps. This occurs because the conjugate acid or base has en depleted through naturalization.
This principle implies that a larger amount of conjugate acid or base will have a greater buffering capacity. Data and Results of Calculations: Moles of HON.. Added before the buffer capacity is exceeded: *Approximately 30. 00 ml of HON.. Added before buffer capacity was exceeded. (graph above) 30. 00 ml HON.. OHO mol HON.. Buffering capacity of trip-basic magnesium phosphate: Buffering capacity- ( Maximum # moles added before buffering capacity is exceeded)/(mass of solid used) = (0. 03 mol g NAACP)= 0. 0011 (mol NAACP)
Discussion of Results: In monophonic acids, the point halfway between the beginning of the curve (before any iterant has been added) and the equivalence point is significant: at that point, the concentrations of the two species (the acid and conjugate base) are equal. Therefore, the Henderson-Washable equation can be solved in this manner: Therefore, one can easily find the peak of the monophonic acid by finding the pH of the point halfway between the beginning of the curve and the equivalence point, and solving the simplified equation.