MHS AP Chemistry
Colligative Properties and Molecular Weight #2
UPDATE THIS LAB!
The purpose of this activity is to determine the molecular weight of an unknown
substance by measuring the boiling point elevaion produced in a known solvent.
The molecular weight will be used to identify the unknown substance.
- The solvent is zzzzzz. The boiling point elevation
constant for this substance is k = xx.x C°/m. The solute will be announced
- Measure the mass and boiling point of zzzzzzz.
- Add some of the unknown solute (no more than about 1/20th of the solvent
mass). Measure the new boiling point, and determine the mass of unknown added.
- Use the formula DT = kfm
[eq. 13.12] and the definition of molality to calculate the molecular weight
of the unknown solute.
- Use the measured molecular weight of your unknown to identify it from the
following list: a, b, c, d, e, f, or g.
- Look up the actual boiling point of pure zzzzzz.
- Each person must pass in their own lab report.
- Each report should have a complete Title Section & Data Table.
- Show every calculation completely & clearly (names, values, and labels).
- Determine the % error in the measured boiling point of pure zzzzzz.
- Determine the % error in the measured molecular weight of your unknown.
- Remember that only data goes in the data table.
This lab is due on ______________. .
[Syllabus 13][MHS AP Chem page]