Here is my data for the lab The bottom portion is just the data reworded Chemica
ID: 697209 • Letter: H
Question
Here is my data for the labThe bottom portion is just the data reworded Chemical Disposal The water remaining in the flask at the end of the experiment may be rinsed down the drain. Any unusecd unknown should be returned to the side bench in the test tube you received it in. Be sure the stopper is in the test tube. Wash your erlenmeyer flask with soap before putting it away Report Calculate the density of the gas in the flask at the point it was sealed Calculate the molar mass of your unknown. Make a correction for the presence of air in the flask originally, and recalculate the Molar mass of your unknown. Discuss factors and assumptions in the iab that limit the accuracy of your result. . . .
Explanation / Answer
1) Mass of the empty flask = 124.9070 g; mass of flask plus cold water = 297.20 g.
Mass of water in the flask = (297.20 – 124.9070) g = 172.293 g.
Density of water = 0.9984 g/cm3.
Volume of water inside the flask = (mass of water)/(density of water) = (172.293 g)/(0.9984 g/cm3) = 172.5691 cm3.
Mass of the unknown in the flask = (mass of flask after heating) – (mass of empty flask) = (125.4376 – 124.9070) g = 0.5306 g.
We will assume that cold water fills up the entire flask and hence, the volume occupied by the cold water is equal to the volume of the flask. The gas will fill up the entire volume of the container as well and hence, the volume occupied by the gas is 172.5691 cm3.
Density of the gas = (mass of unknown)/(volume of flask) = (0.5306 g)/(172.5691 cm3) = 0.0030747 g/cm3 0.003075 g/cm3 (ans).
2) Temperature of the hot water bath = temperature of the gas = 100°C = (273 + 100) K = 373 K.
Atmospheric pressure = 756.10 torr = (756.10 torr)*(1 atm/760 torr) = 0.994868 atm (1 atm = 760 torr).
Volume of the gas in the flask = 172.5691 cm3 = (172.5691 cm3)*(1 mL/1 cm3)*(1 L/1000 mL) = 0.1725691 L (1 cm3 = 1 mL; 1 L = 1000 mL).
Use the ideal gas law: P*V = n*R*T
where P = pressure of the gas; V = volume of the gas; T = temperature of the gas in the Kelvin scale and n = number of moles of the gas. R is the universal gas constant.
Plug in values and obtain
n = P*V/RT = (0.994868 atm)*(0.1725691 L)/(0.082 L-atm/mol.K).(373 K) = 0.00561314 mole.
Molar mass of the gas = (mass of the unknown)/(moles of gas) = (0.5306 g)/(0.00561314 mole) = 94.52819 g/mol 94.5282 g/mol (ans).
3) I need to know the volume or the vapor pressure of the air to perform the calculations.
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