A buffer solution is prepared by mixing 2.50 mL of 2.00M sodium acetate with 3.30mL of 0.500M HCl and diluting the buffer with water to a final volume of 500.0mL. pK acetic acid: 4.76
what is ph of buffer?
what is final concentration of buffer?
acetate = Ac
acetic acid = HAc
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millimols Ac = mL x M = 5.00
mmols HCl = 3.30 x 0.5 = about 1.6
..........Ac + H^+ ==> HAc
I........5.00..1.6.....0
C........-1.6.-1.6.....+1.6
E........3.4....0.....1.6
pH = pKa + log(3.4/1.6)
final (Ac) = millimols/mL = 3.40/5.80=?
final (HCl) = 1.60/5.80 = ?
final concn buffer = M Ac + M HCl
To determine the pH of the buffer, we need to calculate the concentration of the acidic and conjugate base components in the buffer solution.
Step 1: Calculate the moles of sodium acetate (conjugate base).
First, convert the volume of sodium acetate to liters:
2.50 mL = 2.50 mL * (1 L / 1000 mL) = 0.00250 L
Next, calculate the moles of sodium acetate using the molarity:
moles = volume * molarity
moles of sodium acetate = 0.00250 L * 2.00 M = 0.00500 moles
Step 2: Calculate the moles of HCl (acid).
First, convert the volume of HCl to liters:
3.30 mL = 3.30 mL * (1 L / 1000 mL) = 0.00330 L
Next, calculate the moles of HCl using the molarity:
moles = volume * molarity
moles of HCl = 0.00330 L * 0.500 M = 0.00165 moles
Step 3: Determine the amount of acetic acid and conjugate base present in the buffer.
In a buffer solution, the moles of the acid and its conjugate base should be equal. Since sodium acetate is the conjugate base of acetic acid, the moles of acetic acid will also be 0.00500 moles.
Step 4: Calculate the concentrations of acetic acid and sodium acetate in the buffer.
Concentration (Molarity) = moles / volume (in liters)
Acetic acid concentration:
Acetic acid = 0.00500 moles / 0.500 L = 0.010 M
Sodium acetate concentration:
Sodium acetate = 0.00500 moles / 0.500 L = 0.010 M
Step 5: Determine the pH of the buffer.
The Henderson-Hasselbalch equation is used to calculate the pH of a buffer solution:
pH = pKa + log10 ([conjugate base] / [acid])
Given:
pKa of acetic acid = 4.76
[conjugate base] = 0.010 M
[acid] = 0.010 M
pH = 4.76 + log10 (0.010 M / 0.010 M)
pH = 4.76 + log10 (1)
pH = 4.76 + 0
pH = 4.76
Therefore, the pH of the buffer solution is 4.76.
To determine the final concentration of the buffer, we need to find the sum of the concentrations of acetic acid and sodium acetate.
Final concentration of the buffer = [acetic acid] + [sodium acetate]
Final concentration of the buffer = 0.010 M + 0.010 M = 0.020 M
Therefore, the final concentration of the buffer solution is 0.020 M.