Calculating Molar Mass Percent Error in Butane Lab Results

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SUMMARY

The discussion focuses on calculating the molar mass percent error of butane, where a measured value of 20 g/mol was compared to the accepted value of 58.14 g/mol, resulting in a percent error of -70%. The high error is attributed to the conditions under which the accepted value is determined, specifically Standard Temperature and Pressure (STP), and the limitations of accounting for vapor pressure. The conversation emphasizes that without eliminating human error, speculating on the causes of such discrepancies is unproductive.

PREREQUISITES
  • Understanding of gas laws, specifically the Ideal Gas Law (PV=nRT).
  • Familiarity with the concept of Standard Temperature and Pressure (STP).
  • Knowledge of percent error calculation methods.
  • Basic laboratory techniques for collecting gas over water.
NEXT STEPS
  • Research the Ideal Gas Law and its applications in laboratory settings.
  • Study the effects of vapor pressure on gas measurements.
  • Explore methods to minimize human error in experimental procedures.
  • Learn about the significance of STP in chemical calculations.
USEFUL FOR

Chemistry students, laboratory technicians, and educators involved in experimental design and analysis of gas properties.

SkittlesGal
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Homework Statement


I did a lab on the collection of butane over water to calculate the molar mass. In one trial, the measured molar mass was 20 g/mol, however, the accepted value for butane is 58.14 g/mol. This means the percent error is -70%. Why is it so high, assuming there is no relevant human error causing it?


Homework Equations


n=PV/RT
(measured value-accepted value)/accepted value


The Attempt at a Solution


I think it's so high because the accepted value is gathered at STP, and although the vapor pressure was accounted for, it still does not entirely account for the error.
 
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Huge error for a single trial is meaningless. Speculating over what have happened when you can't eliminate human error is a waste of time.
 

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