The student removed the 250-mL Erlenmeyer flask containing the gas vapor to let
ID: 479406 • Letter: T
Question
The student removed the 250-mL Erlenmeyer flask containing the gas vapor to let it cool to room temperature. When the gas had completely condensed, he weighed the flask and the liquid. mass of 250-mL Erlenmeyer flask and liquid 79.118 g What is the mass of the liquid in the flask? What is the molar mass of the unknown liquid in grams per mole? Using Table 1, what is the identity of the unknown liquid? _ Gas laws only apply to ideal gases. Briefly explain why we can use ideal gas law to determine the molar mass of an unknown liquid. The volume of a gas is measured at several temperatures. The moles and pressure of the gas were held constant for each measurement A plot of the volumes versus the temperatures of the gas sample is given below. Which gas law governs the gas behavior depicted in the plot above? _____Explanation / Answer
3]
Mass of the liquid = Mass of flask + liquid - mass of flask = 79.118 - 78.639 = 0.479 gms
4]
PV = nRT
Pressure = 751 torr = 751/760 = 0.988 atm
V = 5.2 ml
PV = nRT ---> Ideal gas equation
PV = mRT/MW [ n = mass / Molar mass]
The temperature of gas in Kelvin is = 99.3 C + 273.15 = 372.45 K
0.988*5.2*10^-3 = 0.479*0.0821*372.45 / Molar mass
Molar mass = 2850.92 gms/mol
5]
Since table 1 is not mentioned ....check with your table
6]
We vapourised the liquid to gaseous state and we are applying the ideal gas equation to the vapour state of the liquid
or
Vapor is the term for a gas produced from the vaporization of a liquid. If it is assumed that the resulting vapor is an ideal gas, then we can use the ideal gas law:
7]
Charles's law is: When the pressure on a sample of a dry gas is held constant, the Kelvin temperature and the volume will be directly related.
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