How Do You Calculate Buffer Capacity in a Mixed Acid-Base System?

[ms. confused]

Ok, I have a problem...
I have a buffer consisting of acetic acid and sodium hydroxide to which I add HCl (solution 1) and NaOH (solution 2). I'm supposed to find the moles of HCl produced and the moles of NaOH produced in each one. I know the volume of acetic acid is 25.00mL and the volume of NaOH to prepare the buffer is 12.95mL. The concentration of acetic acid is 0.1931M and 0.1000M for both standard NaOH and standard HCl. The pH for solution 1 is 4.76 and the pH for solution 2 is 4.77. I've been trying Henderson-Hasselbalch but I'm confused about what information I'm supposed find exactly by using it...I would really appreciate some help on this...thanks.

 

[Aaron Bex]

In order to solve this problem, you will need to calculate the concentrations of the HCl and the NaOH in each solution. To do this, you can use the Henderson-Hasselbalch equation:

pH = pKa + log[base]/[acid]

Where pKa is the acid dissociation constant for acetic acid (4.76).

For solution 1, the concentration of HCl is 0.1000M and the concentration of NaOH is 0.1931M. Plugging these values into the equation above, we get:

4.76 = 4.76 + log[0.1000]/[0.1931]

This means that solution 1 contains 0.1000 moles of HCl and 0.1931 moles of NaOH.

For solution 2, the concentration of NaOH is 0.1000M and the concentration of HCl is 0.1931M. Plugging these values into the equation above, we get:

4.77 = 4.76 + log[0.1000]/[0.1931]

This means that solution 2 contains 0.1000 moles of NaOH and 0.1931 moles of HCl.

 

[Blueshift5]

Hi there,

Thank you for sharing your problem with us. It seems like you are trying to determine the buffer capacity of your solution, which is the ability of a buffer to resist changes in pH when small amounts of acid or base are added.

To calculate the buffer capacity, you will need to use the Henderson-Hasselbalch equation, which relates the pH of a buffer solution to the concentration of the acid and its conjugate base. The equation is as follows: pH = pKa + log([A-]/[HA]), where pKa is the acid dissociation constant, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the acid.

In your case, the acid is acetic acid and its conjugate base is acetate. The pKa for acetic acid is 4.76, which is the same as the pH for solution 1. This means that the concentrations of acetic acid and acetate are equal, and the buffer is functioning at its maximum capacity. To calculate the moles of HCl produced in solution 1, you can use the equation M1V1 = M2V2, where M1 and V1 are the concentration and volume of the acid (HCl) and M2 and V2 are the concentration and volume of the buffer solution (acetic acid and sodium hydroxide).

Similarly, for solution 2, you can use the Henderson-Hasselbalch equation to calculate the buffer capacity and the moles of NaOH produced. The pH for solution 2 is slightly higher than the pKa, which means that the buffer is not functioning at its maximum capacity. This could be due to the addition of NaOH, which is a strong base, and has increased the concentration of the conjugate base (acetate) in the solution.

I hope this helps to clarify your confusion and provides some guidance for finding the moles of HCl and NaOH produced in each solution. If you need further assistance, please don't hesitate to reach out. Good luck with your experiment!