1. Because the mass of the flask with water exceeds the amount that can be weigh
ID: 502442 • Letter: 1
Question
1. Because the mass of the flask with water exceeds the amount that can be weighed on the digital balances, the triple-beam-balance is used, which only weighs to ±0.01 g. Why doesn't using this balance affect the number of significant digits to which the experimental molecular weight of carbon dioxide can be reported?
2.Why can we neglect the mass of the air in the flask when obtaining the mass of the water in the flask (as we do when weighing most things) but not neglect the mass of the air when we calculate the mass of carbon dioxide in the flask?
Explanation / Answer
1. A triple-beam balance is less accurate and is still used for determination of mass as accurate measurement is not required for the calculation of molecular weight.
2. Mass of air in the flask is ignored when obtaining mass of water sice mass of air is relatively small compared to water and does not change the value much. But for measuring mass of carbon dioxide (mass comparable to air), mass of air must be subtracted to avoid error.
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