To 10ml of a 0.10 acetic acid solution a 0.10M NaOH solution is added what is ph of the solution when 9.5ml of NaOH have been added
acetic acid = HAc
sodium acetate = NaAc
millimols HAc = mL x M = 10 x 0.1 -= 1
mmols NaOH = 0.95
............HAc + NaOH ==> NaAc + H2O
I...........1......0........0......0
add..............0.95...............
C........-0.95..-0.95......0.95....
E.........0.05.....0......0.95.....
So you have formed a buffered solution consisting of 0.05 mmols HAc and 0.95 mmols of sodium acetate (NaAc) in 20 mL of solution. Plug that into the Henderson-Hasselbalch equation and solve for pH.
To find the pH of the solution when 9.5 ml of a 0.10 M NaOH solution is added to 10 ml of a 0.10 M acetic acid solution, you need to calculate the concentration of acetic acid (CH3COOH) and the concentration of its conjugate base (CH3COO-) after the neutralization reaction has occurred.
Step 1: Calculate the initial concentration of acetic acid (CH3COOH):
The initial number of moles of CH3COOH in the 10 ml solution is:
0.10 M x 0.010 L = 0.001 mol
Step 2: Calculate the number of moles of NaOH that have reacted:
The number of moles of NaOH used is equal to the concentration of NaOH (0.10 M) multiplied by the volume of NaOH used (9.5 ml):
0.10 M x 0.0095 L = 0.00095 mol
Step 3: Calculate the remaining moles of CH3COOH:
Since NaOH reacts with acetic acid in a 1:1 ratio, the number of moles of CH3COOH remaining is:
0.001 mol - 0.00095 mol = 0.00005 mol
Step 4: Calculate the final volume of the solution:
The final volume of the solution is the sum of the initial volume of acetic acid (10 ml) and the volume of NaOH used (9.5 ml):
10 ml + 9.5 ml = 19.5 ml (or 0.0195 L)
Step 5: Calculate the concentration of acetic acid (CH3COOH) in the final solution:
The concentration of acetic acid in the final solution is equal to the remaining moles divided by the final volume:
Concentration = 0.00005 mol / 0.0195 L
Step 6: Calculate the concentration of the conjugate base (CH3COO-) in the final solution:
The concentration of the conjugate base is equal to the concentration of NaOH used (0.10 M) multiplied by the volume of NaOH used (9.5 ml):
Concentration = 0.10 M x 0.0095 L
Step 7: Use the Henderson-Hasselbalch equation to calculate the pH:
pH = pKa + log([CH3COO-] / [CH3COOH])
The pKa value of acetic acid is approximately 4.75. Plug in the values to calculate the pH.