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A buffer solution contains 0.391 M KHCO_3 and 0.395 M Na_2Co_3. Determine the pH

ID: 501845 • Letter: A

Question

A buffer solution contains 0.391 M KHCO_3 and 0.395 M Na_2Co_3. Determine the pH change when 0.115 mol NaOH is added to 1.00 L of the buffer. pH after addition- pH before addition = pH change = A buffer solution contains 0.370 M CH_3NH_3Cl and 0.373 M CH_3NH_2 (methylamine). Determine the pH change when 0.094 mol NaOH is added to 1.00 L of the buffer. pH after addition pH before addition pH change Determine the pH change when 0.076 mol NaOH is added to 1.00 L of a buffer solution that is 0.302 M in HClO and 0.214 M in CIO^- pH after addition pH before addition = pH change =

Explanation / Answer

Ka2 of H2CO3 = 4.7×10–11

pKa2 = 10.33

pH = pKa + log [Na2CO3 / KHCO3]

    = 10.33 + log [0.395 / 0.391]

pH = 10.33

pH before addition = 10.33

pH = pKa + log [salt + C / acid - C]

     = 10.33 + log [0.395 + 0.115 / 0.391 - 0.115]

     = 10.60

after addition pH = 10.60

pH change = 10.60 - 10.33

pH change = 0.27