ANALYSIS-Show all work, and provide explanations in complete sentences. 1. Your

Question

ANALYSIS-Show all work, and provide explanations in complete sentences. 1. Your unknown hydrocarbon is one of the compounds listed in Table 1. Based on your results for the boiling point and refractive index of your unknown hydrocarbon, which hydrocarbon is most likely to be the identity of your unknown? Why? 2. Suggest a second possible identity of your unknown, and explain why it is your second choice and not your first choice. 3. Assuming that your second choice for the identity were actually correct, suggest two sources of experimental error that caused your results to be as they are. Make sure to explain how the source of error caused the inaccuracy of your results.

Explanation / Answer

The temperature at which the rapid bubbling occurs a few degrees above(2oC to 30C)
the boiling point. If you delayed too much to note down the temperature of the unknown
then I guess it won't be a problem. However if you delayed too much then you may
end up getting wrong results.
1) & 2)
Since you forgot to note down temperature, relying upon the refractive index value
seems to be wise. However your decision seems to be partly right. The compound seems
to be either 3-methyl pentane or 2,4-Dimethyl pentane but not any other compound
between these two. Please consider your unknown B.P while looking for compound.
Choose the componds which are closer to 1.3806 at your unknown boiling point
value.
3) Assume that the second choice is 2,4-Dimethyl pentane, whose boiling point is above
median boiling point.The 2 experimental errors can be
   i) If you considered the observed value directly in Refractometer then you will get wrong
   value of refractive index. So,calculate a corrected refractive index of the unknown.
(observed RI of water - Literature value of RI of water) = correction
   (observed RI of unknown - correction) = corrected RI of the unknown
ii) If you place the thermometer bulb at high position the vapors won’t reach it. Before they
enter into the sidearm, your observed boiling point will be lower than it should be.
If you place the thermometer bulb at low position, vapors of impurities may reach it,
giving a high reading for the boiling point range
  
  

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