a 250.0 ml buffer solution is 0.250 M in acetic acid and. 250M in sodium acetate. what is the ph after addition of. 0050 mol of HCL? what is the ph after the addition of. 0050 mol of NaOH?
See your post above.
To find the pH after the addition of HCl and NaOH, we need to consider how these chemicals will react with the acetic acid and sodium acetate in the buffer solution.
First, let's calculate the change in concentrations of acetic acid (CH3COOH) and sodium acetate (CH3COONa) after the addition of HCl and NaOH.
1. Addition of HCl:
The reaction between HCl and CH3COOH can be represented as:
HCl + CH3COOH ⇌ CH3COOH2+ + Cl-
Since HCl is a strong acid, it will completely dissociate into H+ and Cl-. Therefore, we will have an increase in the concentration of H+. Let's calculate how much the concentration of acetic acid and sodium acetate will change:
Given:
Initial concentration of CH3COOH = 0.250 M
Initial concentration of CH3COONa = 0.250 M
Amount of HCl added = 0.0050 mol
The change in concentration of CH3COOH will be equal to the amount of HCl added:
Change in concentration of CH3COOH = 0.0050 mol / 0.250 L = 0.020 M
The concentration of CH3COOH will increase by 0.020 M, and the concentration of CH3COONa will remain the same.
2. Addition of NaOH:
The reaction between NaOH and CH3COOH can be represented as:
CH3COOH + NaOH ⇌ CH3COONa + H2O
Since NaOH is a strong base, it will completely dissociate into Na+ and OH-. Therefore, we will have an increase in the concentration of OH-. Let's calculate how much the concentration of acetic acid and sodium acetate will change:
Given:
Initial concentration of CH3COOH = 0.250 M
Initial concentration of CH3COONa = 0.250 M
Amount of NaOH added = 0.0050 mol
The change in concentration of CH3COOH will be equal to the amount of NaOH added:
Change in concentration of CH3COOH = 0.0050 mol / 0.250 L = 0.020 M
The concentration of CH3COOH will decrease by 0.020 M, and the concentration of CH3COONa will increase by 0.020 M.
Now that we know the changes in concentration, let's calculate the pH after the addition of HCl and NaOH.
pH after addition of HCl:
The concentration of H+ ions will increase due to the addition of HCl. Since acetic acid is a weak acid, we can assume that a small fraction of it will dissociate into H+ ions and acetate ions (CH3COO-). To calculate the pH, we need to use the Henderson-Hasselbalch equation:
pH = pKa + log([CH3COO-] / [CH3COOH])
The pKa value for acetic acid is 4.75. Substituting the values:
pH = 4.75 + log([0.250 + 0.020] / [0.020])
pH after addition of NaOH:
The concentration of OH- ions will increase due to the addition of NaOH. The reaction between NaOH and CH3COOH will produce CH3COONa and water. Since CH3COONa is a salt of a weak acid, it will hydrolyze to some extent and release OH- ions. To calculate the pH, we need to use the formula:
pOH = pKw - pH = pKb + log([OH-] / [CH3COOH])
The value of pKb for the acetate ion (CH3COO-) is equal to 14 - pKa, which is 14 - 4.75 = 9.25. Using this value and the changes in concentration:
pOH = 9.25 + log([0.250 + 0.020] / [0.020])
To find the pH, we can subtract the pOH value from 14:
pH = 14 - pOH
Now you can calculate the pH after the addition of HCl and NaOH using the derived equations and the given values.