A buffer is prepared using acetic acid, CH3COOH, (a weak acid, pKa = 4.75) and sodium acetate, CH3COONa (which provides acetate ions, the conjugate base), according to the following proportions:
Volume of CH3COOH(aq): 100.0 mL
Concentration of CH3COOH(aq): 1.151 M
Volume of CH3COONa(aq): 113.0 mL
Concentration of CH3COONa(aq): 1.270 M
Use the Henderson-Hasselbalch equation (below) to calculate the pH of the buffer solution.
pH=pKa+log[A−][HA]
equation is pH=pKa+log[A−]/[HA]?
yes
Plug in the numbers and calculate it.
is it just = 4.75+log(1.270/1.151)?
Yes, it's just that.
you dont need to take the volume into consideration?
The formula is pH = pKa + log (base)/(acid)/ Concn is in mols/L which is M
so you substitute the MOLAR CONCENTRATIONS and that's it.
i see, thanks!
i think its this:
Volume of final solution = (100.0 + 113.0) mL = 213.0 mL
[CH₃COOH] = (1.151 M) × (100.0/213.0) = 0.5404 M
[CH₃COO⁻] = (1.270 M) × (113.0/213.0) = 0.6738 M
Henderson-Hasselbalch equation:
pH = pKa + log([CH₃COO⁻]/[CH₃COOH])
pH = 4.75 + log(0.6738/5404)
pH = 4.85