TABLE 16.1 Mass and volume data for titration of primary standard acid and unkno
ID: 1043473 • 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
Table 16.2 :
A. molarity of NaOH
moles H2C2O4.2H2O = mass H2C2O4.2H2O/molar mass H2C2O4.2H2O
molar mass H2C2O4.2H2O = 126.07 g/mol
1 moles NaOH reacted with 1 mole of H2C2O4.2H2O
molarity NaOH = moles NaOH/volume NaOH
Run 1 Run 2 run 3
mass H2C2O4.2H2O 0.1734 0.2542 0.2203
mmol H2C2O4.2H2O 1.375 2.016 1.750
mmol OH- reacted 2.750 4.032 3.500
Volume NaOH (ml) 22.9 22.65 33.94
molarity NaOH (M) 0.120 0.180 0.103
average molarity NaOH = 0.134 M
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B. molecular weight of unknown acid
average molarity NaOH = 0.134 M
moles NaOH = molarity NaOH x volume NaOH
moles acid = moles NaOH/2
molecular weight acid = mass acid/moles acid
Run 1 Run 2 run 3
mass of unknown acid 0.1838 0.1942 0.1829
Volume NaOH (ml) 17.79 18.70 17.50
mmoles NaOH 2.384 2.506 2.345
mmole unknown acid 1.192 1.253 1.1725
molecular weight acid 154.2 155.0 156.0
average molecular weight of acid = 155.07 g/mol
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