Purpose of the experiment

In this experiment, we are assuming an unknown vaporized liquid has ideal gas properties. Based on this we will use the Ideal gas law and stoichiometry to calculate the Molar mass. Based on numeric and qualitative data we might make an assumption as to the identity of the liquid.

Materials

A special round bottomed flask

Aluminum foil

Pipette to transfer unknown liquid

accurate digital scale

A hot water bath setup.

Graduated cylinder

Ice bath setup

Experimental procedure:

We obtain the mass of the empty flask, aluminum foil (both pieces) and rubber band.

To find the volume of the flask, we fill it with water and then transfer that to a graduated cylinder for measurement. Since we are not using a rubber stopper this will provide us with an accurate measurement.

Transfer a small volume of the unknown liquid to the flask.

We immerse the flask in the hot water bath and secure with a clamp to the stand.

We aim to reach a steady boil temperature. The aim is to volatilize the unknown liquid and drive out any air in the flask. At this point we assume the temperature and pressure of the gas has equalized with the surrounding bath and atmosphere (respectively).

We are instructed to allow this to continue for 5 minutes. we then, cover the flask with the second piece of aluminum to trap any gas inside the flask and then plunge the flask in the ice water bath after tempering slightly with cold water.

We can then measure the mass of the condensed liquid.

Measurements and Calculations

Pressure mmHg
767.6

Pressure atm
1.01

R (cm3 atm K-1 mol-1)
82.055

T (C)
98.6

T (Kelvin)
371.75

Volume of flask (ml)
981

mass of flask (g)
78.64

mass of Al foil (1) (g)
0.241

mass of Al foil (2) (g)
0.171

rubber band (g)
0.248

mass of flask+liquid (g)
80.73

mass of liquid(g)
1.434

Mr=mass/moles
Mr = m*R*T PV

Mr = 1.43*82.06*371.75 981*1.01
= 44.14

Conclusion and Error Assessment

Based on molecular mass estimate obtained and other qualitative data; Odor and familiar high solvent effect on nail polish, we guess that the identity of the unknown liquid is Acetone which has a Mr of 58.08

Error