Question

I have two buffers: 1) SODIUM ACETATE PH= 6.48, 0.1M, 0.1 L, PkA=4.76 2) SODIUM PHOSPHATE , Ph=10.04, pka 7.21 What is the ratio of acid/ base in your buffer? How many micromoles of base and acid are presentin the solution?

Answer 1

pH of acidic buffer

1) pH = pka + loga(base(or)salt/acid)

    6.48 = 4.76+log(x)

   x = base/acid = 52.48

where as , acid/base = (1/52.48) = 0.02

no of mole of buffer = M*V = 0.1*0.1 = 0.01 mole

buffer = acid+base

acid = x , base = y

from ratio, acid = 0.02 base

buffer = 0.02*y+y = 0.01

y = no of mole of base = 0.0098 mole

                         = 9800 micro moles

x = no of mole of acid = 0.01-0.0098 = 0.0002 mole

                         = 200 micro moles

2)
pH = pka + loga(base(or)salt/acid)

10.04 = 7.21 +log(x)

   x = base/acid = 676.083

where as , acid/base = (1/676.083) = 0.00148