For each of the following experimental conditions determine whether molar mass would be:
1) too high, B) too low or C) unaffected. In each case, explain how this result occurs
a) after removing the flask from the water bath, the experimenter cools the flask to room temperature but does not dry it. The calculated molar mass will be: A) B) C)
b) the flask is removed form the water bath containing vapor only, the experimenter cools the flask to room temperature and some vapour condenses inside the flask. The calculated molar mass will be: A) B) C)
c) the flask volume is not measured; instead the experimenter assumes the flask volume to be exactly 125.00mL. The calculated molar mass will be: A) B) C)
d) From the time the mass of the unused flask assembly (flask, foil, and elastic band) is recorded the flask is handled several times with oily fingers. The calculated molar mass will be: A) B) C)
a) After removing the flask from the water bath and cooling it to room temperature without drying it, the calculated molar mass will be too high (option A). This occurs because any residual water droplets on the surface of the flask will contribute to the mass measured during the experiment. Since the molar mass is calculated based on the mass of the sample, including the mass of water droplets will artificially increase the calculated molar mass.
b) If the flask is removed from the water bath and cooled to room temperature, and some vapor condenses inside the flask, the calculated molar mass will be too low (option B). This happens because the condensation of vapor inside the flask adds extra mass to the sample, leading to an artificially lower calculated molar mass.
c) If the flask volume is not measured and the experimenter assumes it to be exactly 125.00 mL, the calculated molar mass will be unaffected (option C). This is because the volume of the flask does not directly affect the molar mass calculation, which is based on the mass of the sample and the moles of the substance.
d) If the flask is handled several times with oily fingers after the mass is recorded, the calculated molar mass will be unaffected (option C). This is because the molar mass calculation is based on the mass of the sample and the moles of the substance, and oil residue on the flask does not alter the mass of the substance being analyzed.