PART A $($titration with indicator$)$

Letter of Unknown Acid Mass of Unknown Acid Volume of Equivalence Point

Calculation that shows the number of grams of unknown acid required to consume $25$ mL of standard NaOH titrant.

PART B $($titration with pH meter$)$

Mass of Unknown Acid

Volume of Equivalence Point

Calculation that gives the molar mass of the unknown acid.

Concentration of NaOH pKa of Unknown Acid

$=$ pH at half$-$equivalence volume

Here is a list of potential monoprotic acids. Based on the experimentally derived pKa and molar mass, determine which of the following is your unknown acid.

Acid Name

betaine hydrochloride

sodium hydrogen sulfate monohydrate sulfanilic acid

mandelic acid

ascorbic acid

glutamic acid monohydrate para$-$aminobenzoic acid

picolinic acid

potassium hydrogen phthalate $2-($N$-$morpholino$)$ethanesulfonic acid potassium hydrogen phosphate, monobasic

Molar Mass pKa

$153\mathrm{.}611\mathrm{.}84138\mathrm{.}081\mathrm{.}95173\mathrm{.}193\mathrm{.}25152\mathrm{.}153\mathrm{.}41176\mathrm{.}124\mathrm{.}14165\mathrm{.}154\mathrm{.}28137\mathrm{.}124\mathrm{.}86123\mathrm{.}115\mathrm{.}25204\mathrm{.}235\mathrm{.}46195\mathrm{.}246\mathrm{.}15136\mathrm{.}097\mathrm{.}21$

Note: The molar mass may be more accurate than the pKa. Favor the molar mass if there is a discrepancy, but do not ignore the pKa.

Proposed Identity of the Unknown Acid