Firstly, the student used potassium hydrogen phthalate (KHP, 204.22 g/mol) as standard to determine the exact concentration of the NaOH titrant. The results of the student are summarized in the table below: Note: The stoichiometric relationship of KHP to NaOH is 1:1 Standardization Trial 1 Trial 2 Trial 3 Trial 4 KHP Mass, g 0.5033 0.5066 0.6989 0.6843 Volume NaOH used, mL 24.32 25.61 24.67 24.56 After the standardization, the student weighed different amounts of the unknown acid. In a similar fashion, the student performed acid-base titration using phenolphthalein as indicator. The results of the molecular weight determination are summarized below: Note: The stoichiometric relationship of Unknown acid to NaOH is 1:2 Molecular Weight Determination Trial 1 Trial 2 Trial 3 Trial 4 Unknown Mass, g 0.1234 0.1034 0.1178 0.1322 Volume NaOH used, mL 21.75 20.56 24.39 25.08 The potential unknown given by the professor to the student are as follows: Diprotic acid Fumaric acid Oxalic acid Succinic acid Malonic acid Tartaric acid Citric acid Molecular Weight, g/mol 116.07 90.03 118.09 104.06 150.09 192.12 Considering all the trials in molecular weight determination, what is the average molecular weight of the acid as analyzed by the student? A) 85.00 B) 87.90 C) 81.63 D) 89.09 E) 84.32
trials. Firstly, the student used potassium hydrogen phthalate (KHP, 204.22 g/mol) as standard to determine the exact concentration of the NaOH
titrant. The results of the student are summarized in the table below:
Note: The stoichiometric relationship of KHP to NaOH is 1:1
Standardization Trial 1 Trial 2 Trial 3 Trial 4
KHP Mass, g 0.5033 0.5066 0.6989 0.6843
Volume NaOH used, mL 24.32 25.61 24.67 24.56
After the standardization, the student weighed different amounts of the unknown acid. In a similar fashion, the student performed
using phenolphthalein as indicator. The results of the molecular weight determination are summarized below:
Note: The stoichiometric relationship of Unknown acid to NaOH is 1:2
Molecular Weight
Determination
Trial 1 Trial 2 Trial 3 Trial 4
Unknown Mass, g 0.1234 0.1034 0.1178 0.1322
Volume NaOH used, mL 21.75 20.56 24.39 25.08
The potential unknown given by the professor to the student are as follows:
Diprotic acid Fumaric acid Oxalic acid Succinic acid Malonic acid Tartaric acid Citric acid
Molecular Weight,
g/mol
116.07 90.03 118.09 104.06 150.09 192.12
Considering all the trials in molecular weight determination, what is the average molecular weight of the acid as analyzed by the student?
A) 85.00
B) 87.90
C) 81.63
D) 89.09
E) 84.32
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