5. The melting point of 4-nitrobenzyl alcohol is reported as 94 C and the meltin

Question

5. The melting point of 4-nitrobenzyl alcohol is reported as 94 C and the melting point of triphenylmethane is reported as 94. Which statement most accurately reflectsthe expected result for the melting point of a 50:50 mixture of the two? a. The mixture will have a melting point of 94 °C b. The mixture will have a melting point above 94 °C c. The mixture will have a melting point below 94 °C d. No prediction can be made about the melting point. 6. If you submit two conformations (A and B) for an Equilibrium Geometry calculation using the Hatree-Fock 3-21 G* method and determine that A has a total energy of-36.4425 a.u and B has a total energy of-47.3324 a.u., which conformation is more stable? a. A c. Can't be determined from the information available. 7. Which of following statements concerning boiling points is true? a. Boiling points decrease with increasing molecular weight in a homologous series of molecules b. The boiling point of any liquid at higher elevation is higher. c. Liquids with higher vapor pressures have lower boiling points than liquids with lower vapor pressures. d. Using one of the boiling point techniques that we learned is a way to purify a liquid sample. 8. In which of the following solvents would you expect Ibuprophen (structure shown below) to be soluble? OH a. HaO b. IM HCI c. IM NaOH d. None of the above 9. Which of the following would increase the retention time for a pure compound during analysis by gas chromatography? a. Decreasing the flow rate of the inert gas b. Increasing the temperature of the column. c. Injecting twice as much sample d. a and c 10. Hexane has a refractive index of 1.3749. If the hexane is contaminated with an unknown liquid, how will this affect the refractive index? aThe refractive index will not change. b. The refractive index will be higher than 1.3749. cThe refractive index will be lower than 1.3749. d. None of these predictions can be made about the refractive index.

Explanation / Answer

Q5

if we mix both species, then

they should melt about hte same range,

since it is 94x1 + 94x2 if x1 = X2, then total PMP = 94

note tht the MP decreases only if the volatile species and impurities have lower BP, then you will expect a dorp in melting point

choose C

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