1. Mar 31, 2004

### tiffany

Hi! Dear members, I am new here..I hope to make many friends amongst you all...I will keep the intros short..since I need help by tonight I have a few questions regarding the Ideal Gas Law and calculating the molar mass as well as percent yeild..please help!

Here they are:

1.) The procedure for this experiment was used for a single trial and resulted in the following data. THe mass of the empty flask with the dry foil cap was 55.441g. The sample was heated in water at 99.5 degress Celsius then allowed to condense. The flask and condensed vapor weighed 56.039g. To determine the volume of the flask, it was filled with water giving a mass of 270.9g. The barometric pressure in the lab was 752mmHg. Use this data to find the Molar Mass of the sample unknown. Show all steps and unit conversions involved. Use 0.9982g/ml for water density.

I came to an answer...I calculated that the molar mass is .998moles

Is that right? I really appreciate your input!

Ok 2nd questions has four parts:

Below is a list of some errors that could occur during the experiment. For each error, consider the effect on the data that would be obtained and trace the effect through to the calculation of molar mass. Indicate whether the calculation will yeild a higher or loewr value than the actual molar mass. Then explain your reasoning for each case in detail. (Note: Assume the sample had the molar mass as the result in question 1.)

a.) A student removed the sample from the heating bath before the sample had all evaporated.

b.) A student did not dry the outside of the flask after removing it from the water bath to weigh the flask with condensed vapor.

c.) After the heating process, the sample had not yet condensed when the foil caps were switched.

d.) During the heat operation, the flask was left in the hot water bath very long past the time when it had all evaporated.