Calculating the pH of a Buffer Solution

An acidic buffer solution is made up of a weak acid HA and its salt (M+A ), where H denotes the presence in the molecule of hydrogen atoms which can form ions, and M+ refers to a (usually) metal ion  

In a buffer mix the value of [HA] is effectively the initial concentration, of the acid since weak acids are only very slightly dissociated, and [A ] is effectively the initial concentration of the salt because it is completely ionised. 

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Hasselbalch equation, which is used to calculate the pH of a buffer solution as shown in the next section. 

PROBLEM 16.9 Use the Henderson-Hasselbalch equation to calculate the pH of a buffer solution prepared by mixing equal volumes of 0.20 M NaHC03 and 0.10 M Na2C03. (,Ka values are given in Appendix C.)... 

Calculate the pH of a buffer solution containing 0.05 M acetic acid and 0.1 M sodium acetate. The pKa of acetic acid is 4.74. The ionic strength of the solution is 0.10 M. 

Calculating the pH of a Buffer Solution Following the Addition of a Strong Acid or Strong Base. 

On the AP exam, acid-base questions appear on a regular basis, and buffer calculations are among the most common of those questions to pop up. One of the things you are expected to be able to do is calculate the pH of a buffer solution, and though you may not realize it yet, you have already done this calculation. In the previous example of the common ion effect, when you calculated the pH of the solution made with the 0.30 M acetic acid and the 0.30 M sodium acetate, that was a buffer solution. That is the first type of buffer calculation you are expected to know. The second type of calculation is to determine the effect of adding a strong acid or base to a buffer, and the... 

Calculate the pH of a buffer solution in which both the acetic acid and sodium acetate concentrations are 1.00 X 10 M. The equilibrium constant, Xa, for acetic acid is 1.75 X 10 . 

Calculate the pH of a buffer solution similar to that described in Example 9.9 except that the acid concentration is doubled, while the salt concentration remains the same. 

A buffer solution can be described by an equilibrium-constant expression. The equilibrium-constant expression for an acidic system can be rearranged and solved for [H3O+]. In that way, the pH of a buffer solution can be obtained, if the composition of the solution is known. Alternatively, the Henderson-Hasselbalch equation, derived from the equilibrium constant expression, may be used to calculate the pH of a buffer solution. 

Calculate the pH of a buffer solution prepared by dissolving 21.5 g benzoic acid (HC7H5O2) and 37.7 g sodium benzoate In 200.0 mL of solution. 

Mathematical Calculate the pH of a buffer solution that contains 0.10 Macetic acid (Table 2.6) and 0.25 Msodium acetate. 

In Sample Exercise 17.3 we calculated the pH of a buffered solution. Often we will need to work in the opposite direction by calculating the amounts of the add and its conjugate base needed to achieve a specific pH. This calculation is illustrated in Sample... 

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