5) Using the results from your titration curve of the unknown acid and by referr

Question

5) Using the results from your titration curve of the unknown acid and by referring to Table 5.4, identify your samples identity Sample number: Identity of unknown sample: Table 5.4 List of possibilities for the unknown compound Mol. Wt. pk, (g/mol) PK, Compound Formula Tartaric acid (diprotic) CH,0 150.1 2.98 Potassium hydrogen tartrate Ko,CCH(OH)CH(OH)CO,H 188.2 4.34 Potassium hydrogen phthalateHOCOC, H.COOK 204.2 5.41 di-Sodium hydrogen citrateNa,HC,H,0,1VH,0 263.1 6.38 61.83 9.24 (HOCH)CNH, HCI 1576 8.13 TRISHCI Boric acid H,B03

Explanation / Answer

The change in PH when a strong acid is titrated with a strong base ,when a weak acid is titrated with a strong base and when a weak base is titrated with a strong acid ,Each will have a characteristic shape when the titration curve is plotted ,that is,the pH is plotted on y-axis and the volume of added titrant is plotted on x-axis .A titration curve allows one to experimentally determine the Ka for a weak acid or Kb for a weak base . The pH will be mesured using a Ph probe attached to a CBL and graphing calculator .

The primary purpose of this experiment is to identify an unknown acid by finding its molecular weight . The acid is titrated with NaOH solution of known concentration.Molecular weight(or molar mass) is found in g/mole of the acid.Weighting the original sample of acid will tell its mass in grams. Moles can be determined from the volume of NaOH titrant needed to reach the first equivalent point .The volume and concentration of NaOH titrant are used to calculate moles of NaOH . Moles of unknown acid equals moles of NaOH at the first equivalent point . Once grams and moles of the acid are known molecular weight can be calculated in g/mole.

Then from the list given to you ,identification of the unknown acid is quite possible

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