p. Concentration of Unknown Acid Trial Tried 3 Trial volume or unknown acid Aver

Question

p. Concentration of Unknown Acid Trial Tried 3 Trial volume or unknown acid Average molario of NaOH from above mL or Naori ar equivalence point Molarity of unknown acid Average mollarity show ations Standard deviation QUESTIONS 1. what are the largest sources oferror in this experiment? 2. what is the pll of the solution obtained 30.00 mL of o 125 NaOH? by mixing 30 oo mL of o 250 M HCI and We assume additive volumes. 3. What is the pH of a solution that is 0.75 M in sodium acetate and 0.50 M in acetic acid? (Ka for ace acid is 1.8x10

Explanation / Answer

1.largest source of error will be incorrect standardization of NaOH.

2. moles of HCl = 0.25 M * 0.03 L =0.0075 moles

moles of naOH = 0.125 M * 0.03 L = 0.00375 moles

excess HCl = 0.0075-0.00375 = 0.00375 moles

Molarity of the excess HCl = 0.00375 moles /total volume in L = 0.0625 M

pH = -log [H+] = 1.2

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pka = -logka = 4.74

pH = pka + log [acetate/acetic acid]

     = 4.74 + log [0.75/0.50] = 4.92

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