the measured ph is 5.18 for a solution containing 25.0 ml 1.0 m nach3coo and 10.0 ml 1.0 m ch3cooh. calculate the corresponding value of ka for acetic acid.
To calculate the corresponding value of Ka for acetic acid, we need to use the Henderson-Hasselbalch equation.
The Henderson-Hasselbalch equation relates the pH of a solution to the pKa (the negative logarithm of Ka) and the ratio of the concentrations of the acid and its conjugate base.
The equation is:
pH = pKa + log([A-]/[HA])
In this case, acetic acid (CH3COOH) is the weak acid, and its conjugate base is acetate ion (CH3COO-).
Given information:
pH = 5.18
Volume of sodium acetate (NaCH3COO) solution = 25.0 mL
Volume of acetic acid (CH3COOH) solution = 10.0 mL
First, we need to calculate the concentrations of both the acid and its conjugate base.
Concentration of NaCH3COO:
Initially, we have 25.0 mL of 1.0 M NaCH3COO. By dilution, we can calculate the concentration:
Concentration of NaCH3COO = [(initial volume)(initial concentration)] / final volume
= [(25.0 mL)(1.0 M)] / (25.0 mL + 10.0 mL)
= 0.714 M
Concentration of CH3COOH:
Since CH3COOH has the same concentration as NaCH3COO (1.0 M), its concentration is also 0.714 M.
Now, we can substitute these values into the Henderson-Hasselbalch equation:
5.18 = pKa + log([CH3COO-]/[CH3COOH])
The pKa value for acetic acid is 4.76.
Therefore, we can rewrite the equation as:
5.18 = 4.76 + log([0.714]/[0.714])
Simplifying further:
5.18 - 4.76 = log(1)
0.42 = log(1)
Since log(1) equals zero, we can conclude that:
0.42 = 0
However, this result is not possible, and it indicates an error in the calculation or data.
Please double-check the given information or let us know if there are any other details that need to be considered.