Question

What is the ph of a buffer consisting of 0.200 m hc2h3o2 and 0.200 m kc2h3o2? the k a for hc2h3o2 is 1.8×10−5. view available hint(s) what is the ph of a buffer consisting of 0.200 m hc2h3o2 and 0.200 m kc2h3o2? the k a for hc2h3o2 is 1.8×10−5. 7.00 0.70 2.72 4.74?

Answer 1

pH = pKa + log $\frac{[base]}{[Acid]}$
Acid  is HC₂H₃O₂ and conjugate base is KC₂H₃O₂,
pKa = - log Ka = - log (1.8 x 10⁻⁵) = 4.74
so pH = 4.74 + log (0.2/0.2) = 4.74
This is called maximum buffer capacity (when acid conc. and base conc. are equal) the pH = pKa in this case