Calculating the pH of buffers

This relation, known as the Henderson-Hasselbalch equation, is often used in biology and biochemistry to calculate the pH of buffers. Historically, it was Henderson who discovered Equation 14.1 in 1908. Hasselbalch put it in logarithmic form eight years later. 

The Henderson-Hasselbalch equation, which is used to calculate the pH of buffer solutions, is frequently encountered in the biological literature and biochemical texts. It is obtained by expressing each term in Equation 9-29 in the form of its negative logarithm and inverting the concentration ratio to keep all signs positive ... 

Many assumptions are required to use these equations, but other methods of calculating the pH of buffers are too difficult to appear on an examination and are beyond the scope of high school chemistry. Therefore, if you are asked for the pH of a buffer solution on the teacher certification exam, you can use the buffer equation with confidence. 

Equation 17.9 is known as the Henderson-Hasselbalch equation. Biologists, biochemists, and others who work frequently with buffers often use this equation to calculate the pH of buffers. In doing equilibrium calculations, we have seen that we can normally n ect the amounts of the acid and base of the buffer that ionize. Therefore, we can usually use the starting concentrations of the acid and base components of the buffer directly in Equation 17.9. 

Beyond its usual application in calculating the pH of buffer solutions, the Henderson-Hasselbalch equation can be rearranged to tell us the ratio of concentrations of an acid and its conjugate base at a particular pH. 

Calculate the pH of buffers that contain the acid and conjugate base concentrations hsted below. 

This equation is often employed to calculate the pH of buffered solutions, although for our purposes we will rearrange the equation in the following way ... 

As in Example 6.13, the Henderson-Hasselbalch equation provides a simple way to calculate the pH of a buffer and to determine the change in pH upon adding a strong acid or strong base. 

Any solution containing comparable amounts of a weak acid, HA, and its conjugate weak base, A-, is a buffer. As we learned in Chapter 6, we can calculate the pH of a buffer using the Henderson-Hasselbalch equation. 

It. A buffer is prepared by dissolving 0.0250 mol of sodium nitrite, NaN02, in 250.0 mL of 0.0410 M nitrous acid, HN02. Assume no volume change after HN02 is dissolved. Calculate the pH of this buffer. 

Suppose we dissolve 1.2 g of sodium hydroxide (0.030 mol NaOH) in 500. mL of the buffer solution described in Example 11.1. Calculate the pH of the resulting solution and the change in pH. Assume that the volume of the solution remains unchanged. 

Use the seven-step strategy to calculate the pH of the buffer solution using the buffer equation. Then compare the amount of acid in the solution with the amount of added base. Buffer action is destroyed if the amount of added base is sufficient to react with all the acid.The buffering action of this solution is created by the weak acid H2 PO4 and its conjugate base HP04. The equilibrium constant for this... 

Buffers are solutions that resist a change in pH when we add an acid or base. A buffer contains both a weak acid (HA) and its conjugate base (A-). The acid part will neutralize any base added and the base part of the buffer will neutralize any acid added to the solution. We may calculate the hydronium ion concentration of a buffer by rearranging the Ka expression to yield the Henderson-Hasselbalch equation, which we can use to calculate the pH of a buffer ... 

These equations allow us to calculate the pH of the buffer solution knowing the Ka of the weak acid or Kb of the weak base and the concentrations of the weak acid and its conjugate base. If we know the desired pH along with the Ka of the... 

The common-ion effect is an application of Le Chatelicr s principle to equilibrium systems of slightly soluble salts. A buffer is a solution that resists a change in pH if we add an acid or base. We can calculate the pH of a buffer using the Henderson-Hasselbalch equation. We use titrations to determine the concentration of an acid or base solution. We can represent solubility equilibria by the solubility product constant expression, Ksp. We can use the concepts associated with weak acids and bases to calculate the pH at any point during a titration. 

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