Please help!!
Given this data:
mass of unknown acid 1.4671g
Volume of NaOH used in titration 18.47mL
Concentration of the NaOH used 0.2403M
pH of the original acid solution 2.16
pH of the final acid solution 3.49
Show me how do I calculate the Ka of the unknown acid and the concentration of undissociated acid from pH measurements? and
How do I calculate the total concentration of Unknown acid from pH measurements?
If this helps answer, I have already found the molecular weight to be 165.3 g/mol
the molarity of unknown acid solution from titration is 0.1774 M
Thank you so much to whoever replies...
Is the 18.47 mL base used the amount to titrate to the equivalence point. Is the pH at the equivalence point 3.49 or is that some other point on the titration curve? I don't get a molar mass of 165.3 from the data above. Is there more data? I suspect so. Please type the entire question.
To calculate the Ka of the unknown acid and the concentration of undissociated acid from pH measurements, we can use the Henderson-Hasselbalch equation. The Henderson-Hasselbalch equation relates the pH of a solution to the pKa and the ratio of the concentration of the conjugate base to the concentration of the acid.
The Henderson-Hasselbalch equation is defined as:
pH = pKa + log([A-]/[HA])
Where pH is the pH of the solution, pKa is the acid dissociation constant, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the acid.
Since we are given the pH of the original acid solution and the final acid solution, we can use these values to calculate pKa and the ratio [A-]/[HA].
To calculate the Ka of the unknown acid, we need to convert the pH values into concentrations of [A-]/[HA]. We can do this by converting the pH values into hydrogen ion concentrations (H+).
To convert a pH into a hydrogen ion concentration, you can use the equation:
[H+] = 10^(-pH)
Now, let's calculate the concentration of [HA] and [A-] from the pH values:
[H+]original = 10^(-pHoriginal)
[H+]final = 10^(-pHfinal)
Since the original acid solution is fully dissociated into HA and A-, and the final acid solution contains only HA, we can use the difference in [H+] between the original and final acid solutions to calculate the concentration of [A-]. This can be done by subtracting [H+]final from [H+]original:
[A-] = [H+]original - [H+]final
Now that we have calculated [A-], we can calculate [HA] using the fact that the total concentration of the unknown acid is equal to the sum of [A-] and [HA]:
[HA]total = [A-] + [HA]
Since we know the total concentration of the unknown acid from the titration (0.1774 M), we can substitute this value to find the concentration of [HA]:
0.1774 M = [A-] + [HA]
Now, we have the values for [A-] and [HA]. We can substitute these values and the pH values into the Henderson-Hasselbalch equation to solve for pKa:
pHoriginal = pKa + log([A-]/[HA])
With this equation, we can rearrange it to solve for pKa:
pKa = pHoriginal - log([A-]/[HA])
Now, we have the value for pKa, which is the acid dissociation constant. This will give us information about the strength of the acid.
To calculate the concentration of undissociated acid, we can use the equation:
[HA] = [HA]total - [A-]
By substituting the values we have, we can find the concentration of undissociated acid.
I hope this explanation helps you in calculating the Ka of the unknown acid, concentration of undissociated acid, and the total concentration of the unknown acid.