I am laughing this question because I have no clue and I don\'t know why profess

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I am laughing this question because I have no clue and I don't know why professor gave me this nut question. It would be great if you can help me with this question... many thanks

There are five hydrocarbon compounds (compounds of C and H) that have the formula C_6H_14. All are liquids at room temperature but have slighty different densities.

Hydrocarbon:
Hexane (d = 0.6600 g/mL)
2,3 Dimethylbutane (d = 0.6616 g/mL)
2-Methylpentane (d = 0.6532 g/mL)
2,2-DIMETHYLBUTANE (d = 0.6485 g/mL)
2-Methylpentane (d = 0.6645 g/mL)

a. You have a pure sample of one of these hydrocarbon and to identify it you decide to measure its density. You determine that a 5.0 mL sample (measured in a graduated cylinder) has a mass of 3.2745 g (measured on an analytical balance.) Assume that the accuracy of the values for mass and volume is plus or minus one (+/-1) in the last significant figure. What is the density of the liquid?
b. Can you identify the unknown hydrocarbon based on your experiment?
c. Can you eliminate any of the five possibilities based on the data? If so, which one (s)?
d. You need a more accurate volume measurement to solve this problem, and you redetermine the volume to be 4.93 mL. Based on these new data, what is the unknow compound?

Explanation / Answer

a) density = mass/volume = 3.2745 g/5.0 mL = 0.6549 +/- 0.0002 g/mL (you add uncertainty when multiplying or dividing) b) Based on the density in part a, it is difficult to exactly determine the hydrocarbon (none of the densities above fall within the limits of uncertainty: 0.6547 to 0.6551). The most likely candidate based on the answer to part a) is 2-Methylpentane (d = 0.6532 g/mL). c) You cannot really eliminate any answers because when we take uncertainty into account, the largest possible measurement you can get is 33.2746 g/4.9 mL = 0.6683 g/mL. The smallest possible measurement you can get is 33.2744 g/5.1 mL = 0.6420 g/mL. All density values for the above hydrocarbons fall between these extrema. d) density = mass/volume = 3.2745 g/4.93 mL = 0.6642 +/- 0.0002 g/mL. Based on this data, 2-Methylpentane (d = 0.6645 g/mL) is the unknown.

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