Question

How would each of the following procedural errors affect the results to be expected in this experiment? Give your reasoning in each case.
(A) Not all of the liquid was vaporized when the flask was removed from the water bath.
(B) The flask was not dried before the final weighing with the condensed vapor inside.
(C) The flask was left open to the atmosphere while it was being cooled, and the stopper was inserted just before the final weighing.
(D) The flask was stoppered and removed from the bath before the vapor had reached the temperature of the boiling water. All the liquid had vaporized.

Answer 1

Answer:

a) if the liquid is not vaporized completely, then the condensed vapor in the flask contains the air which is initially occupied before the liquid is heated. When calculating the molar mass of the vapor the moles of air which are initially present are not excluded, so that the molar mass of the vapor would be an increase in value.

b) While weighing the condensed vapor, the flask should be dried. If the weighing flask is not dried then the water which is layered on the surface of the flask is also added to the mass of the vapor. Therefore, the mass of the vapor that is calculated would be increase.

c) When condensing the vapor, the stopper should not be removed from the flask, because the vapor will escape from the flask and a small amount of vapor will condense in the flask. Therefore, the mass of the condensed vapor would be In small value.

d) If all the liquid is vaporized, when the flask is removed before the vapor had reached the temperature of boiling water, then the boiling

temperature of that liquid would be lower than that of the boiling temperature of the water.Therefore, the liquid may have more volatility.