Hi could someone please help me in the next 5 minutes with this question:
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 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
and the Ka of the unknown acid is 0.000324
Thank you so much to whoever replies...
To calculate the concentration of undissociated acid from pH measurements, you can use the Henderson-Hasselbalch equation:
pH = pKa + log([A-]/[HA])
Where pH is the measured pH of the solution, pKa is the negative logarithm of the acid dissociation constant, [A-] is the concentration of the dissociated acid (conjugate base), and [HA] is the concentration of the undissociated acid.
From the given data, we have the pH of the original acid solution (2.16) and the pH of the final acid solution (3.49). We can calculate the concentration of undissociated acid using the Henderson-Hasselbalch equation and the known values.
First, let's calculate the pKa. We know that pKa = -log(Ka), so we can plug in the given Ka value (0.000324) to calculate pKa.
pKa = -log(0.000324) ≈ 3.49
Now, we can rearrange the Henderson-Hasselbalch equation to solve for [HA]:
pH = pKa + log([A-]/[HA])
[HA] = 10^(pH - pKa)
[HA] = 10^(2.16 - 3.49) ≈ 0.0268 M
Therefore, the concentration of undissociated acid is approximately 0.0268 M.
To calculate the total concentration of the unknown acid from pH measurements, we need to consider the dissociation of the acid. The concentration of the dissociated acid ([A-]) can be calculated using the concentration of the undissociated acid ([HA]).
Since the total concentration of the unknown acid is the sum of the concentration of undissociated acid and the concentration of dissociated acid, we can write:
[Unknown acid] = [HA] + [A-]
However, since the dissociation constant (Ka) of the acid is very small (0.000324), we can assume that the concentration of [HA] is approximately equal to the total concentration of the unknown acid.
Therefore, the total concentration of the unknown acid is approximately 0.0268 M.