The Interdisciplinary Laboratory

 Pre-Lab Assignment for Experiment #4:
Molecular Weight of Macromolecules

The first portion of the laboratory requires the synthesis of several mixtures of agar agar and gelatin.  In all cases you seek to make mixtures whose total weight is 2.250 g.  Calculate the weights of agar agar and gelatin necessary to make 5 wt% gelatin and 30 wt% gelatin mixtures.  Assume you have weighed out the weights to calculated to an uncertainty of 1 mg.  What is the uncertainty in wt % s of your mixtures? 

You will also need to make solutions for viscosity measurements.  Suppose you weigh 0.100 g of a polymer mixture and dissolve this weight in water, diluting the solution to the mark in a 100 mL volumetric flask.  Assume an uncertainty in the weight of 1 mg and an uncertainty in the volume of your dilution of 0.1 mL.  What is the uncertainty in your concentration?  Suppose you weigh your polymer sample to an uncertainty of 0.1 mg and the uncertainty in the volume was 0.08 mL.  What is the uncertainty in your concentration in this case?  Dilutions of this solution will be necessary for viscosity experiments.  What will be the uncertainty in a solution prepared from the one just described if 10.00 mL were diluted to 100.00 mL?   Let the uncertainty in the volumetric pipet used to deliver the 10.00 mL be 0.08 mL and the uncertainty in the volumetric flask volume be 0.1 mL.

Due to Professor Van Hecke (Gerald_VanHecke@hmc.edu) by 7 pm Monday 27 Oct for Group 2B and by 7 pm Monday 17 Nov for Group 2A.  Be prepared to turn in your calculations at the start of the laboratory period.  Please send your answers as straight email rather than attachments and please put your name in the body of your message.