Question

The ph of a sodium acetate-acetic acid buffer is 4.70. calculate the ratio [ch3coo−] / [ch3cooh]

Answer 1

According to Henderson–Hasselbalch Equation,

                                    pH  =  pKa + log [Acetate] / [Acetic Acid]

As,      pKa of Acetic Acid  =  1.76

So,                               pH  =  1.76 + log [Acetate] / [Acetic Acid]

                                  4.70  =  1.76 + log [Acetate] / [Acetic Acid]

                        4.70 - 1.76  = log [Acetate] / [Acetic Acid]

                                 -0.04  =  log [Acetate] / [Acetic Acid]

Taking Antilog on both sides,

               [Acetate] / [Acetic Acid]  =  0.912