Chemistry help needed please???

Question

The pH of a bicarbonate-carbonic acid buffer is 7.70. Calculate the ratio of the concentration of carbonic acid (H2CO3) to that of the bicarbonate ion (HCO3-).

Ka H2CO3 = 4.2*10^-7

Kb HCO3- = 2.4*10^-8

10 points for best answer!!!

Answer 1

pH = pKa + log (base/acid).  What you want is (acid/base) so you do 7.7-6.38=log base/acid.  10^(-1.32)=base/acid.  1/.0479= acid/base=20.89