Question

Calculate the following buffer solutions. A buffer solution was made by dissolving 10.0 grams of sodium acetate in 200.0 mL of 1.00 M acetic acid. Assuming the change in volume when the sodium acetate is not significant, estimate the pH of the acetic acid/sodium acetate buffer solution. The Ka for acetic acid is 1.7 x 10-5. Calculate the ratio of ammonium chloride to ammonia that is required to make a buffer solution with a pH of 9.00. The Ka for ammonium ion is 5.6 x 10-10. After completing the calculations answer the following questions 1) Is the pH of the solution consistent with the Ka or is there a better Ka that could be used? 2) If 100 mL of buffered solution is used, what is the pH change if 20 mL of 0.5M HCl is added? Does the pH change exceed the buffering capacity of the solution? Explain 3) If 100 mL of buffered solution is used, what is the pH change if 20 mL of 0.5M NaOH is added? Does the pH change exceed the buffering capacity of the soltuion? Explain

Answer 1

In this response, we explain how to calculate the pH of an acetate buffer using the Henderson-Hasselbalch equation. We also provide the steps to calculate the ratio of ammonium chloride to ammonia for a buffer with a pH of 9.00. Finally, we discuss the effect of adding HCl and NaOH to the buffer solution and how it relates to the buffering capacity.

Step-by-step explanation:

Calculating the pH of an acetate buffer

To calculate the pH of an acetate buffer, we need to determine the concentration of acetic acid and its salt, sodium acetate. The pH can be determined using the Henderson-Hasselbalch equation, pH = pKa + log([salt]/[acid]). In this case, pKa is the negative logarithm of the acid dissociation constant (Ka) for acetic acid, which is 1.7 x 10-5. The concentration of the salt, [salt], is determined by dissolving 10.0 grams of sodium acetate in 200.0 mL of 1.00 M acetic acid. The concentration of the acid, [acid], is 1.00 M. Plugging the values into the Henderson-Hasselbalch equation, we can calculate the pH of the buffer.

Ratio of ammonium chloride to ammonia for a buffer with pH 9.00

To calculate the ratio of ammonium chloride (NH4Cl) to ammonia (NH3) for a buffer with pH 9.00, we need to use the Henderson-Hasselbalch equation again. This time, we know the pH and the Ka for ammonium ion (NH4+), which is 5.6 x 10-10. Rearranging the equation, we can solve for the ratio of [salt]/[acid] needed to achieve the desired pH.

Effect of adding HCl and NaOH to the buffer solution

To determine the pH change when adding 20 mL of 0.5 M HCl or 0.5 M NaOH to 100 mL of the buffered solution, we need to consider the buffering capacity of the solution. The buffer capacity depends on the concentrations of the acid and salt in the buffer. If the pH change is within the range of the buffering capacity, the pH change will be minimal. If it exceeds the buffering capacity, the pH change will be significant.