Calculations
1. For each polymer solution, report the concentration, c (in gm PVOH per 100 mL of solution)
and the viscosity, η, you measured. This can be conveniently done in a table.
2. Always include uncertainties. Give estimates of:
• The relative uncertainty in each concentration, ∆c/c. Is this a negligible error?
• The relative uncertainty in each viscosity.
3. Plot ηsp/c versus c for the uncleaved and the cleaved polymer. Give indications of error as
solid error bars on your graphs for each measurement, and report the values you plotted in
tabular form in the Results section.
4. From analyses of these plots obtain [η] for each material. Record the uncertainty limits on
[η] (obtained by propagation of uncertainty) in your Results section.
5. Calculate Mv and Mn for the original polymer and the degraded polymer. Always report
uncertainties with the values.
6. From the molar-mass results, obtain a value for ∆. Report this value and any uncertainty in
it.
IMPORTANT: Clean glassware and SVM3000 thoroughly after use; your grade may
depend on it. If glassware or the SVM3000 is found to contain polymer, the grade of
the group who used it last will be lowered. Do not let this happen to you!
Experiment 5, page 8 Version of November 9, 2005
Discussion Questions
1. What are the principal commercial uses of poly(vinyl alcohol)?
2. Write out a general equation for the cleavage reaction of poly(vinyl alcohol).
3. Cleavage occurs only at 1,2 glycol structures, but two successive backward additions do not
result in two 1,2 glycol structures. How is this taken into account in the calculation of ∆?
4. A statistical fit to ηsp = Ac + Bc2
might be an appropriate way to analyze for [η]. Carry out
this analysis on your data for the uncleaved polymer, and compare the answer to that
determined by plotting ηsp/c versus c. In your view, which procedure is more accurate?
Explain.
5. Does the uncertainty in [η]cleaved or the uncertainty in [η]uncleaved contribute more to the
uncertainty in ∆? Explain.
6. Are systematic errors important in this experiment? If so, identify any sources of systematic
error and provide estimates of how significant they may be.
Calculations
1. For each polymer solution, report the concentration, c (in gm PVOH per 100 mL of solution)
and the viscosity, η, you measured. This can be conveniently done in a table.
2. Always include uncertainties. Give estimates of:
• The relative uncertainty in each concentration, ∆c/c. Is this a negligible error?
• The relative uncertainty in each viscosity.
3. Plot ηsp/c versus c for the uncleaved and the cleaved polymer. Give indications of error as
solid error bars on your graphs for each measurement, and report the values you plotted in
tabular form in the Results section.
4. From analyses of these plots obtain [η] for each material. Record the uncertainty limits on
[η] (obtained by propagation of uncertainty) in your Results section.
5. Calculate Mv and Mn for the original polymer and the degraded polymer. Always report
uncertainties with the values.
6. From the molar-mass results, obtain a value for ∆. Report this value and any uncertainty in
it.
IMPORTANT: Clean glassware and SVM3000 thoroughly after use; your grade may
depend on it. If glassware or the SVM3000 is found to contain polymer, the grade of
the group who used it last will be lowered. Do not let this happen to you!
Experiment 5, page 8 Version of November 9, 2005
Discussion Questions
1. What are the principal commercial uses of poly(vinyl alcohol)?
2. Write out a general equation for the cleavage reaction of poly(vinyl alcohol).
3. Cleavage occurs only at 1,2 glycol structures, but two successive backward additions do not
result in two 1,2 glycol structures. How is this taken into account in the calculation of ∆?
4. A statistical fit to ηsp = Ac + Bc2
might be an appropriate way to analyze for [η]. Carry out
this analysis on your data for the uncleaved polymer, and compare the answer to that
determined by plotting ηsp/c versus c. In your view, which procedure is more accurate?
Explain.
5. Does the uncertainty in [η]cleaved or the uncertainty in [η]uncleaved contribute more to the
uncertainty in ∆? Explain.
6. Are systematic errors important in this experiment? If so, identify any sources of systematic
error and provide estimates of how significant they may be.
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