What is the pH of. buffer solution that is 0.266 M in lactic acid (C_3H_8O_3) an

Question

What is the pH of. buffer solution that is 0.266 M in lactic acid (C_3H_8O_3) and 0.111 M in. sodium lactate (NaC_3H_5_3, )? The Ka of lactic acid is 1.4 times 10^-4 14.38 10.53 5.38 3.47 4.23 A 10.00 mL of NaOH is completely neutralized by titration with 28.3 mL of 0.187 M H_3PO_4. Calculate the concentration of the NaOH. 0.159 M 0.176 M 0.529 M 1.59 M What is the [H_3O^+] for a solution at 25 degree C that has pH = 5.640? A) 2.34 times 10^-4 M 2.29 times 10^-6 M 4.37 times 10^-19 M 4.27 times 10^-11 M 8.36 M What is the [OH^-] for a solution at 25 degree C that has [H_2O^+l = 8.23 times 10^-2M? > 10^-5M 1.22 times 10^-6 M 8.23 times 10^-12 M 1.22 times 10^23M 8.23 times 10^-16 M What is the pH of a 0.0125 M NaOH solution? 0.972 1.903 12.097 13.028 none of the above

Explanation / Answer

1. pH of acidic buffer = pka + log(salt/acid)

   pka = -logka = -log(1.4*10^-4) = 3.85

    pH = 3.85+log(0.111/0.266)

       = 3.47

answer: D) 3.47

2)

H3PO4 + 3 NaOH ---> Na3PO4 + 3H2O

1 mole H3PO4 = 3 mole NaOH

M1V1/n1 = M2V2/n2

28.3*0.187/1 = (10*M1/3)

M1 = molarity of NaOH = 1.59 M

answer: D) 1.59 M

3) [H3O+] = 10^-pH

          = 10^-5.64

    = 2.29*10^-6 M

answer: B

4) [OH-] = KW/[H3O+]

         = 10^-14/(8.23*10^-2)

        = 1.22*10^-13 M

answer: D

5) pH of base = 14 - (-log(OH-))

               = 14 - (-log0.0125)

               = 12.097

answer: C

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