Name of unknown:Methanol Mass Total volume Molar Mass of flask/foil/band pressur

Question

Name of unknown:Methanol Mass Total volume Molar Mass of flask/foil/band pressure boiling flask/foil/ condensate of vapor (mL) vapor g/mol) Trial Mass empty Measured Water Mass (kPa) temp('C) band& g) condensate cooled (g) 198.086 96.12 98.2 98.224 281.788 96.12 98.3 81.920 382.081 96.10 98.3 82.211 147.1 148.9 149.0 MEAN Molar Mass (g/mol) Standard Deviation Show one sample calculation of the mass of condensate and Molar Mass here luse Equation 7.1k make sure to show any unit conversions done with collected data

Explanation / Answer

trial 1.

total mass of condensate = mass of condensate + all the bands , plate etc - mass of all the bands , plate etc

= 98.224 - 98.086 = 0.138g

similarly for other 2

2.

81.920 - 81.788 = 0.132g

3.

82.211 - 82.081 = 0.13g

moles of each vapour = n = PV/RT = 101325 Pa x 147.1 x 10-6 m3 / 8.314 Pa.m3/mol.K x (98.2+273.15) = 0.00482765 mol

mass of condensate / moles = molar mass = 0.138g / 0.00482765 mol = 28.585334 g/mol

2nd trial

101325 Pa x 148.9x 10-6 m3 / 8.314 Pa.m3/mol.K x (98.3+273.15) = 0.0048854 mol

molar mass = 0.132g / 0.0048854 mol = 27.01928 g/mol

3rd trial

101325 Pa x 149.0 x 10-6 m3 / 8.314 Pa.m3/mol.K x (98.3+273.15) = 0.00488868 mol

molar mass = 0.13g / 0.00488868 mol = 26.592045 g/mol

Mean molar mass = (M1 + M2 + M3 ) / 3 = 27.39888 g/mol

The variance of a set of values, which we denote by 2, is defined as 2 = summation (x x¯)2 /(n-1)

standard deviation = root(2)

x¯ = mean value

x = taken value at that point

{(28.585334 g/mol - 27.39888 g/mol)2 +(27.01928 g/mol - 27.39888 g/mol)2 + (26.592045 g/mol - 27.39888 g/mol)2}/(3-1)

= 1.101

standard deviation = root(1.101) = 1.049

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