What is the percent dissociation of ascorbic acid if the solution has a pH = 5.50 and a pKa= 4.10?
The answer is 96% but I keep getting 1500%
Why don't you show your work and let me find the error? |That would have saved a lot of time.
To determine the percent dissociation of ascorbic acid, we need to use the Henderson-Hasselbalch equation and the concept of acid dissociation.
The Henderson-Hasselbalch equation is given by:
pH = pKa + log([A-]/[HA])
Where:
- pH is the measure of acidity or basicity of the solution.
- pKa is the negative logarithm (base 10) of the acid dissociation constant (Ka).
- [A-] is the concentration of the conjugate base.
- [HA] is the concentration of the undissociated acid.
In this case, we are given:
- pH = 5.50
- pKa = 4.10
To solve for the percent dissociation, we need to find the ratio of the conjugate base ([A-]) to the undissociated acid ([HA]).
First, we need to determine the ratio of [A-]/[HA] from the Henderson-Hasselbalch equation. Rearranging the equation, we have:
[A-]/[HA] = 10^(pH - pKa)
Substituting the given values:
[A-]/[HA] = 10^(5.50 - 4.10)
[A-]/[HA] = 10^1.4
Calculating this:
[A-]/[HA] = 25.11886432
Now, the percent dissociation can be calculated using the formula:
Percent Dissociation = ([A-]/([A-] + [HA])) * 100
Substituting the values:
Percent Dissociation = (25.11886432 / (25.11886432 + 1)) * 100
Percent Dissociation = (25.11886432 / 26.11886432) * 100
Percent Dissociation = 0.960861 * 100
Percent Dissociation ≈ 96.09%
Therefore, the correct answer is approximately 96%, not 1500%.