TABLE 16.1 Mass and volume data for titration of primary standard acid and unkno
ID: 1042915 • Letter: T
Question
TABLE 16.1 Mass and volume data for titration of primary standard acid and unknown acid with sodium hydroxide. Run 1 Run 2 Run 3 A Mass of weighing paper (g) 38093370 3220 Mass of weighing paper and ??:04.2 H20 (g) Initial reading of buret (mL) .1 2.llo 1,05 26.7 24.8l 34.99 Run 1 Run 2 Run 3 , 2-.25 n,2-,252-25 Final reading of buret (mL) B Unknown number2 Mass of unknown acid suggested for titration (g) Number of reactive protons per molecule of unknown acid Mass of weighing paper (g) Mass of weighing paper and unknown 3813 .383%2 Initial reading of buret (mL) 2.89 Final reading of buret (mL)Explanation / Answer
A)
Molar mass of H2C2O4.2H2O = 126.0654 g/mol
For Run 1,
Mass of H2C2O4.2H2O used (g) = 0.1734
Moles of H2C2O4.2H2O (mmol) = 0.1734 * 1000 / 126.0654
= 1.3755
Moles of protons reacted(mmol) = Moles of H2C2O4.2H2O (mmol) * No. of protons available for reaction
= 2.7510
Moles of OH- which reacted (mmol) = 2.7510 (Acid base neutralization)
Volume of NaOH solution (mL) = 22.9
Molarity of NaOH solution (M) = 2.7510 / 22.9
= 0.12 M
Similarly for run 2 & 3 we get,
A
Run 1
Run 2
Run 3
Mass of H2C2O4.2H2O used (g)
0.1734
0.2542
0.2203
Moles of H2C2O4.2H2O (mmol)
1.3755
2.0164
1.7475
No. of protons available for reaction
2
2
2
Moles of OH- which reacted (mmol)
2.7510
4.0328
3.4950
Volume of NaOH solution (mL)
22.9
22.65
33.94
Molarity of NaOH solution (M)
0.120
0.178
0.103
Average molarity of NaOH solution (M)
0.134
B)
For run 1,
Mass of unknown acid used (g) = 0.1838
Volume of NaOH solution (mL) = 17.79
Moles of NaOH which reacted (mmol) = 17.79 * Average molarity of NaOH solution (M) in part A
= 17.79 * 0.134 = 2.38
Moles of unknown acid (mmol) = Moles of NaOH which reacted (mmol) / No. of protons available for reaction
= 2.38 / 2 = 1.19
Molecular weight of unknown acid (g/mol) = Mass of unknown acid used (g) * 1000 / Moles of unknown acid (mmol)
= 0.1838 * 1000 / 1.19
= 155.39
Similarly for run 2 & 3 we get,
B
Run 1
Run 2
Run 3
Mass of unknown acid used (g)
0.1838
0.1942
0.1829
Volume of NaOH solution (mL)
17.79
18.70
17.50
Moles of NaOH which reacted (mmol)
2.38
2.50
2.34
No. of protons available for reaction
2
2
2
Moles of unknown acid (mmol)
1.19
1.25
1.17
Molecular weight of unknown acid (g/mol)
154.53
155.33
156.32
Average MW of unknown acid (g/mol)
155.39
A
Run 1
Run 2
Run 3
Mass of H2C2O4.2H2O used (g)
0.1734
0.2542
0.2203
Moles of H2C2O4.2H2O (mmol)
1.3755
2.0164
1.7475
No. of protons available for reaction
2
2
2
Moles of OH- which reacted (mmol)
2.7510
4.0328
3.4950
Volume of NaOH solution (mL)
22.9
22.65
33.94
Molarity of NaOH solution (M)
0.120
0.178
0.103
Average molarity of NaOH solution (M)
0.134
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.