A chemical-process engineer must choose a C6H14 isomer as a nonpolar solvent for an…
CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
A chemical-process engineer must choose a C6H14 isomer as a nonpolar solvent for an industrial extraction. The process requires rapid solvent removal by evaporation after extraction and also occasional operation at elevated pressures, where solvent-solvent attractions affect viscosity.
Isomers of C6H14 include:
• n-hexane
• 2-methylpentane
• 3-methylpentane
• 2,2-dimethylbutane
• 2,3-dimethylbutane
(a) Propose which isomer is expected to have the weakest London dispersion forces. Justify your choice in terms of both polarizability and molecular surface area.
(b) Identify the isomer likely to possess the strongest London dispersion forces. Provide the same type of justification.
(c) For the isomer chosen in part (a), predict qualitatively how its surface tension and viscosity at 25 °C compare with those of the isomer chosen in part (b). Support your answer by discussing intermolecular attractions.
(d) The engineer considers adding one C=C double bond to the isomer chosen in part (b) while keeping the carbon skeleton the same. Predict how this modification would affect (i) the boiling point and (ii) the compressibility factor (Z) of the resulting fluid at high pressures. Provide reasoning grounded in molecular interactions.