Mass of dry, air-filled 250-mL Erlenmeyer flask + stopper Mass of flask + stoppe

Question

Mass of dry, air-filled 250-mL Erlenmeyer flask + stopper Mass of flask + stopper + natural gas Volume of water in flask Air temperature in lab Barometric pressure _____ in Hg _____ mm Hg = _____ atm Density of dry air at current laboratory temperature and pressure _____ (from Table 10.1) Mass of air in flask _____ show calculation: Mass of empty flask + stopper Mass of natural gas Molar mass of natural gas (Show calculation of Trial 1) Average molar mass of natural gas _____ Percent deviation (Show calculation) _____

Explanation / Answer

Q4.

T = 21°C = 21+273 = 284 K

Q5.

P = 762.8 mm Hg = 762.8/760 = 1.00368 atm

Q6.

D of air from:

D = P*MW/(RT) = 1.00368*29/(0.082*294) = 1.20734 g/L

Q7.

mass of air in flask:

volume of flask air --> 250 mL

mass = D*V = 0.250*1.20734 = 0.301835 g of air

Q8.

mass of empty flask + stopper --> 139.42 - 0.301835 = 139.118 g

Q9.

Mass of natural gas:

139.31 -139.118 = 0.192 g

139.31 -139.118  = 0.192 g

139.32 -139.118 = 0.202 g

Molar Mass:

PV = nRT

n = PV/(RT) = (1.00368*0.25) / (0.082*294) = 0.0104081moles

MW = mass/mol

MW1 = (0.192 )/0.0104081 = 18.44 g/mol

MW2 = (0.192 )/0.0104081 = 18.44 g/mol

MW3 = (0.202)/0.0104081 = 19.407 g/mol

Average =(18.44 +18.44+19.407 )/3 = 18.76233 g/mol

deviation = 0.5553

% Dev = 0.5553/18.76233 *100 = 2.95%

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