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Your Task In this investigation you will monitor the pH of an unknown diprotic acid solution as it is titrated with a standardized sodium hydroxide solution. Using the pH curve, you will determine the molar mass and identity of the unknown acid From the following list of five diprotic acids. You should confirm the identity by comparing the pH at the half-equivalence points with the accepted pKa1 and pKa2 values. Diprotic Acid Oxalic Acid Formula H2C2O4 Molecular weight 90 g/mol Ka1 Ka2 6.0 x 10-2 6.1 x 10-5 Malonic Acid H2C3H2O4 104 g/mol 1.5 x 10-3 2.0 x 10-6 Maleic Acid H2C4H2O4 116 g/mol 1.2 x 10-2 5.9 x 10-7 Malic Acid H2C4H4O5 134 g/mol 3.5 x 10-4 6.3 x 10-6 Tartaric Acid H2C4H4O6 150 g/mol 1.0 x 10-3 4.6 x 10-5 Guiding Question What is the identity of an unknown diprotic acid? Supporting Calculations. Include an annotated sample calculation showing how you determined the molar mass of the unknown diprotic acid (i.e. How did you find the equivalence point, and use that value to calculate the molar mass of the unknown acid?). Include an annotated calculation showing how you determined the Ka₁ and Kaz (i.e. How did you find Ka1 and Ka2?). Provide a percent error comparing your experimental molar mass to the accepted value. File Home Insert Page Layout Formulas Data Review View Help Cut Copy Calibri 11 AA == Wrap Text General v Paste BIU A Merge & Center $% 9000 Conditional Format as Format Painter Formatting Table Clipboard 5 Font 5 Alignment Number S Styles B11 X ✓ fx 22.5 A B C D E F G H I J K L M N 1 pH 2 Moles NaOH 3 Moles Unknown Acid 4 Molarity Unknown Acid 5 Total Moles Acid 6 Molar Mass of Acid + 7 Initial NaOH (mL) 42.5 8 Initial pH 2.91 9 Volume 1st half 7.5 10 Volume 1st EP 12.5 11 Volume 2nd half 22.5 12 Volume 2nd EP 26.5 13 14 15 16 17 18 19 20 21 22 23 First Equivalence Point Time: 114 s pH: 5.06 Second Equivalence Point Time: 200 s pH: 8.96 2200.0 6370 T Time 0

Your Task In this investigation you will monitor the pH of an unknown diprotic acid solution as it is titrated with a standardized sodium hydroxide solution. Using the pH curve, you will determine the molar mass and identity of the unknown acid From the following list of five diprotic acids. You should confirm the identity by comparing the pH at the half-equivalence points with the accepted pKa1 and pKa2 values. Diprotic Acid Oxalic Acid Formula H2C2O4 Molecular weight 90 g/mol Ka1 Ka2 6.0 x 10-2 6.1 x 10-5 Malonic Acid H2C3H2O4 104 g/mol 1.5 x 10-3 2.0 x 10-6 Maleic Acid H2C4H2O4 116 g/mol 1.2 x 10-2 5.9 x 10-7 Malic Acid H2C4H4O5 134 g/mol 3.5 x 10-4 6.3 x 10-6 Tartaric Acid H2C4H4O6 150 g/mol 1.0 x 10-3 4.6 x 10-5 Guiding Question What is the identity of an unknown diprotic acid? Supporting Calculations. Include an annotated sample calculation showing how you determined the molar mass of the unknown diprotic acid (i.e. How did you find the equivalence point, and use that value to calculate the molar mass of the unknown acid?). Include an annotated calculation showing how you determined the Ka₁ and Kaz (i.e. How did you find Ka1 and Ka2?). Provide a percent error comparing your experimental molar mass to the accepted value. File Home Insert Page Layout Formulas Data Review View Help Cut Copy Calibri 11 AA == Wrap Text General v Paste BIU A Merge & Center $% 9000 Conditional Format as Format Painter Formatting Table Clipboard 5 Font 5 Alignment Number S Styles B11 X ✓ fx 22.5 A B C D E F G H I J K L M N 1 pH 2 Moles NaOH 3 Moles Unknown Acid 4 Molarity Unknown Acid 5 Total Moles Acid 6 Molar Mass of Acid + 7 Initial NaOH (mL) 42.5 8 Initial pH 2.91 9 Volume 1st half 7.5 10 Volume 1st EP 12.5 11 Volume 2nd half 22.5 12 Volume 2nd EP 26.5 13 14 15 16 17 18 19 20 21 22 23 First Equivalence Point Time: 114 s pH: 5.06 Second Equivalence Point Time: 200 s pH: 8.96 2200.0 6370 T Time 0

Principles of Modern Chemistry
Principles of Modern Chemistry
8th Edition
ISBN:9781305079113
Author:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler
Publisher:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler
Chapter15: Acid–base Equilibria
Section: Chapter Questions
Problem 57P
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Your Task In this investigation you will monitor the pH of an unknown diprotic acid solution as it is titrated with a standardized sodium hydroxide solution. Using the pH curve, you will determine the molar mass and identity of the unknown acid From the following list of five diprotic acids. You should confirm the identity by comparing the pH at the half-equivalence points with the accepted pKa1 and pKa2 values. Diprotic Acid Oxalic Acid Formula H2C2O4 Molecular weight 90 g/mol Ka1 Ka2 6.0 x 10-2 6.1 x 10-5 Malonic Acid H2C3H2O4 104 g/mol 1.5 x 10-3 2.0 x 10-6 Maleic Acid H2C4H2O4 116 g/mol 1.2 x 10-2 5.9 x 10-7 Malic Acid H2C4H4O5 134 g/mol 3.5 x 10-4 6.3 x 10-6 Tartaric Acid H2C4H4O6 150 g/mol 1.0 x 10-3 4.6 x 10-5 Guiding Question What is the identity of an unknown diprotic acid? Supporting Calculations. Include an annotated sample calculation showing how you determined the molar mass of the unknown diprotic acid (i.e. How did you find the equivalence point, and use that value to calculate the molar mass of the unknown acid?). Include an annotated calculation showing how you determined the Ka₁ and Kaz (i.e. How did you find Ka1 and Ka2?). Provide a percent error comparing your experimental molar mass to the accepted value. File Home Insert Page Layout Formulas Data Review View Help Cut Copy Calibri 11 AA == Wrap Text General v Paste BIU A Merge & Center $% 9000 Conditional Format as Format Painter Formatting Table Clipboard 5 Font 5 Alignment Number S Styles B11 X ✓ fx 22.5 A B C D E F G H I J K L M N 1 pH 2 Moles NaOH 3 Moles Unknown Acid 4 Molarity Unknown Acid 5 Total Moles Acid 6 Molar Mass of Acid + 7 Initial NaOH (mL) 42.5 8 Initial pH 2.91 9 Volume 1st half 7.5 10 Volume 1st EP 12.5 11 Volume 2nd half 22.5 12 Volume 2nd EP 26.5 13 14 15 16 17 18 19 20 21 22 23 First Equivalence Point Time: 114 s pH: 5.06 Second Equivalence Point Time: 200 s pH: 8.96 2200.0 6370 T Time 0
Transcribed Image Text:Your Task In this investigation you will monitor the pH of an unknown diprotic acid solution as it is titrated with a standardized sodium hydroxide solution. Using the pH curve, you will determine the molar mass and identity of the unknown acid From the following list of five diprotic acids. You should confirm the identity by comparing the pH at the half-equivalence points with the accepted pKa1 and pKa2 values. Diprotic Acid Oxalic Acid Formula H2C2O4 Molecular weight 90 g/mol Ka1 Ka2 6.0 x 10-2 6.1 x 10-5 Malonic Acid H2C3H2O4 104 g/mol 1.5 x 10-3 2.0 x 10-6 Maleic Acid H2C4H2O4 116 g/mol 1.2 x 10-2 5.9 x 10-7 Malic Acid H2C4H4O5 134 g/mol 3.5 x 10-4 6.3 x 10-6 Tartaric Acid H2C4H4O6 150 g/mol 1.0 x 10-3 4.6 x 10-5 Guiding Question What is the identity of an unknown diprotic acid? Supporting Calculations. Include an annotated sample calculation showing how you determined the molar mass of the unknown diprotic acid (i.e. How did you find the equivalence point, and use that value to calculate the molar mass of the unknown acid?). Include an annotated calculation showing how you determined the Ka₁ and Kaz (i.e. How did you find Ka1 and Ka2?). Provide a percent error comparing your experimental molar mass to the accepted value. File Home Insert Page Layout Formulas Data Review View Help Cut Copy Calibri 11 AA == Wrap Text General v Paste BIU A Merge & Center $% 9000 Conditional Format as Format Painter Formatting Table Clipboard 5 Font 5 Alignment Number S Styles B11 X ✓ fx 22.5 A B C D E F G H I J K L M N 1 pH 2 Moles NaOH 3 Moles Unknown Acid 4 Molarity Unknown Acid 5 Total Moles Acid 6 Molar Mass of Acid + 7 Initial NaOH (mL) 42.5 8 Initial pH 2.91 9 Volume 1st half 7.5 10 Volume 1st EP 12.5 11 Volume 2nd half 22.5 12 Volume 2nd EP 26.5 13 14 15 16 17 18 19 20 21 22 23 First Equivalence Point Time: 114 s pH: 5.06 Second Equivalence Point Time: 200 s pH: 8.96 2200.0 6370 T Time 0
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