Q: Calculate the pH of a solution that is 0.56 M HC3H5O3 and 1.28 M NaC3H5O3.

I used the H-H equation for this and got this so far:
HC3H5O3 acid
NaC3H5O3 base
pH = pKa + log([NaC3H5O3]/[HC3H5O3])
= -log(Ka of HC3H5O3) + log(1.28/0.56)
= -log(1.4*10^-4) + log(1.28/0.56)
A: pH = 4.2129
However, I'm not sure about the Ka of HC3H5O3 or if it's correct, since I just found it online. Can someone check my numbers?

Most of your numbers are correct, i suggest you check brainly.com and submit your question.

I think 4.74 is a better number for pKa of acetic acid. Also, I submit that Jiskha.com is as good as any other site for checking issues.

To calculate the pH of a solution containing a weak acid and its conjugate base, you're on the right track with the Henderson-Hasselbalch equation. However, to accurately determine the pH, you need the correct Ka value for HC3H5O3 (acetic acid). The Ka value you found online is not accurate.

The Ka value for acetic acid (HC2H3O2) is known and is 1.8 x 10^-5. Since acetic acid (HC3H5O3) is the same except for an additional H atom, we can assume that its Ka value would be similar.

Let's recalculate the pH using the correct Ka value:

pH = pKa + log([NaC3H5O3]/[HC3H5O3])
= -log(Ka of HC3H5O3) + log(1.28/0.56)
= -log(1.8 x 10^-5) + log(1.28/0.56)

Calculating this gives us:
pH ≈ 4.77

Therefore, the pH of the solution is approximately 4.77.

To calculate the pH of a solution, you correctly used the Henderson-Hasselbalch equation, which relates the pH to the pKa of the acid and the ratio of its conjugate base to the acid. Let's go step by step and verify the numbers.

1. Determine the pKa of HC3H5O3:
The pKa represents the acidity constant of the acid and can be found in reference tables or online. You mentioned a value of 1.4 x 10^-4, so we will proceed with that.

2. Plug the values into the equation:
pH = pKa + log([NaC3H5O3]/[HC3H5O3])
= -log(1.4 x 10^-4) + log(1.28/0.56)

3. Calculate the log term:
log(1.28/0.56) ≈ 0.4565

4. Calculate the negative logarithm:
-log(1.4 x 10^-4) ≈ 3.8539

5. Add the values together:
pH ≈ 3.8539 + 0.4565 ≈ 4.3104

Therefore, the calculated pH of the solution is approximately 4.3104.

It appears that your calculation is slightly different, resulting in a pH of approximately 4.2129. This difference may be due to rounding errors or variations in the pKa value used.

To ensure accuracy, it is recommended to use more precise values for the pKa and double-check your calculations. Additionally, if you have access to experimental data or a lab protocol, it is always best to verify the value of pKa and the concentration of the solution before performing calculations.