For this question answer the fitted boiling point of pure ethanol: ____ K. 4 sig. fig. Thre rest ? marks in the tale will be answered in the next two questions. Copy the data into Excel and use trendline to fit or calculate the average values for this and the next 2 questions. Sample # Sugar (g)
(This question and the next 2 questions are breakdowns of the same question) A student John wanted to measure the molar mass of an unknown material (UM) via the boiling point change of a solvent. He chose a solvent, ethanol, that can dissolve the material and sugar. He wanted to use sugar (MW = 342.3 g/mol) as a reference sample to get an ebullioscopic constant for his system to reduce the effect of other measuring errors such as pressure, measuring errors, and impurity of the samples. He made 10 solutions each contain 100 g of ethanol and various amont of solute as list in the table. He fits the two sets of data and obtain the molar weight of the unknown materials.
For this question answer the fitted boiling point of pure ethanol: ____ K. 4 sig. fig. Thre rest ? marks in the tale will be answered in the next two questions. Copy the data into Excel and use trendline to fit or calculate the average values for this and the next 2 questions.
| Sample # | Sugar (g) | B.P. (K) | Sample # | UM (g) | B.P. (K) |
| 1 | 0 | 351.2 | 6 | 0 | 351.5 |
| 2 | 5.00 | 351.6 | 7 | 5.00 | 352.0 |
| 3 | 10.00 | 351.9 | 8 | 10.00 | 352.6 |
| 4 | 20.00 | 352.4 | 9 | 20.00 | 353.4 |
| 5 | 50.00 | 353.0 | 10 | 50.00 | 356.5 |
| MW sugar 342.3 g/mol, EtOH 100 g for all samples. | Use the Kb fitted from the sugar samples for the MW of UM. | ||||
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fitted average Kb = __?___ K kg/mol fitted pure EtOH B.P. = ____?___ K |
MW of UM = _____?___ g/mol |
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