Question

"which solution has the lowest ph?" a buffer made with 0.10 m acetic acid and 0.01 m sodium acetate a buffer made with 0.10 m acetic acid and 0.10 m sodium acetate a buffer made with 0.01 m acetic acid and 0.10 m sodium acetate a buffer made with 0.01 m acetic acid and 0.01 m sodium acetate all of the buffers have the same ph since they are all made with acetic acid and sodium acetate.

Answer 1

The answer is a) the PH of a buffer with 0.1 acetic acid and 0.01 m sodium acetate has the lowest PH.

we are going to use H-H equation:

when the formula is:

PH = Pka + ㏒[conjugate base/ weak acid]

when we have Ka of acetic acid = 1.8 x 10^-5

∴Pka = -㏒Ka

         = -㏒ 1.8 X 10^-5

         = 4.7

a) the PH  of a buffer with 0.1 m acetic acid and 0.01 m sodium acetate is:

PH = Pka + ㏒[conjugate base / weak acid]

PH = 4.7 + ㏒[0.01/0.1]

      = 3.7

b) PH of a buffer with 0.1 m acetic acid and 0.1 m sodium acetate is:

PH = Pka + ㏒[conjugate base / weak acid]

PH = 4.7 + ㏒ [0.1 / 0.1]

      = 4.7

c) PH of a buffer with 0.01 m acetic acid and 0.1 m sodium acetate is:

when PH = Pka + ㏒[conjugate base/weak acid]

PH = 4.7 + ㏒ [0.1 / 0.01]

      = 5.7  

d) PH of a buffer with 0. 01 M acetic acid and 0.01 M sodium acetate is :

when PH =  Pka + ㏒(conjugate base/weak acid)

          PH = 4.7 + ㏒ (0.01 / 0.01)

                = 4.7

as the PH pf B and D have the same PH and A has the lowest PH