Acid base help?

Question

the titrationcurve was determined that at midpoint in the buffer region the ph was 4.50. what are pKa and Ka, please shows me work. thanks in advance

Answer 1

ph=pka+log(base/acid)
at midpoint base=acid
ph=pka+log1
so pka=ph=4.5
pka=-logka
ka=10^(-4.5)
typing the number then you got the answer