WILL RATE!!! What effect would each of the following have on the calculated mola
ID: 800580 • Letter: W
Question
WILL RATE!!!
What effect would each of the following have on the calculated molar mass of an unknown.
a) The balance was not zeroed before the three weighings of the test tube, sample, water were made. This caused each mass measurement to be 0.102 g greater than it should have been.
b) The thermometer consistently read 0.06 C lower than it should have, over the entire experimental range
c) The masses of the unknown and the solvent (water) were determinded, and the unknown completely dissolved in the water. Just before the jacketed test tube containing the unknown solution was placed in the ice-salt water bath, a small amount of the solution was spilled out of the tube.
d) The unknown contained a smal amount of an insoluble impurity
e) The unknown contained a small amount of a soluble impurity, which had a molar mass lower than that of the pure unknown.
f) A portion of the unknown did not dissolve.
Explanation / Answer
a) If the balance is not zeroed, then your final molar mass will have the weight of the test tube, sample and water included and there will not be an easy way to calculate just the molar mass of the unknown.
b) temperature and molar mass are proportional. If you are reading the temperature lower than it really is, then your mass will be lower than it really is.
c) Whichever tube lost the solution will have a different weight when compared to the other two test tubes. The molar mass will change due to the lost portion of sample
d) the initial molar mass will be heavier than the final molar mass unless you also add the mass of the insoluble impurity.
e) The total molar mass will be higher than the molar mass of the unknown
f) The molar mass will not change here as mass is not state dependant
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