how do I obtsin the standar deviation of molar mass and felative deviation of mo
ID: 545631 • Letter: H
Question
how do I obtsin the standar deviation of molar mass and felative deviation of molae mass (%RSD) based on these calculations? please explain
Molar Mass of a Volatile Liquid Date A. Preparing the Sample Unknown number Lab Sec. Name Desk No Trial I Trial 2 Trial 3 1. Mass of dry flask, foil, and rubber band (g) B. Vaporize the Sample 1. Instructor's approval of apparatus 2ero ig MAIE C )31215313 16 4 3uB K 3. Mass of dry flask, foil, rubber band, and vapor (g) C. Determine the Volume and Pressure of the Vapor 1. Volume of 125-mL flask (L) 2. Atmospheric pressure (torr, atm) D. Calculations 1. Moles of vaporer (mol) 2. Mass of vapor, mpr (g) 3. Molar mass of compound (g/mol) 4. Average molar mass (g/mol) 5. Standard deviation of molar mass 6. Relative standard deviation of molar mass (&RSD;) Show the calculation for the standard deviation and the relative standard deviation (as %RSD) of the molar mass of the Data Analys Data Analys Data Analys unknown. Data Analysis, C and D Experiment 12 17S 121Explanation / Answer
Average of moles of vapor = ((3.76 +3.757+3.746)/3) mol = 3.75 mols
Average Mass of vapor = ((0.198 +0.116+0.117)/3) g = 0.144 g
Average Molar mass of vapor = g/moles = ((0.0576+0.0308+0.0317)/3) g/mol = 0.0400 g/mol
5. Standard deviation : mean = sum of all values/3 = 0.0400 g/mol
variance = (sum of (mean - Trial 1 value)^2)/3
= [(0.0400-0.0576 )+(0.0400-0.0308)+(0.0400-0.0317)]^2/3
= (0.0031 +0.0000846+0.000069)/3
= 0.00108 g/mol
standard deviation = sq.rt.(0.00108)
= 0.03293
6. Relative standard deviation,
max(0.004+ 0.03293) + min(0.004 - 0.03293)/2 = 0.4%
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