Separation of Cyclohexane and Toluene via Simple Distillation Notes

Source and Background

  • The material is based on the "Separation by Distillation" experimental procedure.
  • Source: Labflow, Catalyst Education, 2020 (www.labflow.com).
  • Context: This is a modified version of the Labflow procedure, adjusted due to material availability and time constraints.

Apparatus Assembly and Preparation

  • Required components for the simple distillation setup:
    • One $125\,cm^3$ flat bottom flask (reaction flask).
    • One thermometer.
    • A simple distillation apparatus.
    • Joint lubricant (to be used if necessary).
    • A hotplate for the heat source.
    • Receiving containers: Two $100\,cm^3$ beakers.
  • Labeling of receiving containers:
    • Container #1 should be labeled: Cyclohexane.
    • Container #2 should be labeled: Toluene.
  • Pre-start checks:
    • All joints must be lubricated if required.
    • The instructor must review and approve the setup before heating begins.
    • Ensure all joint connections are firmly and securely attached.

Reagents and Solution Preparation

  • Reaction Flask Contents:
    • A volume of $30.0\,cm^3$ of a cyclohexane/toluene mixture.
    • $5$ to $6$ boiling beads.
  • Purpose of boiling beads:
    • They facilitate the mixing of the solution by "bouncing around" within the reaction flask as the mixture is heated.

Heating and Monitoring Process

  • Heating procedure:
    • Activate the hotplate to bring the solution to a gentle boil.
    • Monitor the temperature continuously throughout the heating process.
    • Maintain a gentle boil; do not overheat the solution, as this will lead to invalid results.
  • Research task during heating:
    • While the solution is heating, research and record the literature boiling point ranges in degrees Celsius ($^{\circ}C$) for both cyclohexane and toluene.

Distillation of Cyclohexane (First Distillate)

  • Collection Protocol:
    • Place Container #1 (Cyclohexane) under the receiving end of the distillation apparatus.
    • Monitor the thermometer closely for the first appearance of liquid drops in the container.
  • The first distillate is identified as "pure" cyclohexane separated from the mixture.
  • Data Recording for Cyclohexane:
    • Record the starting temperature at which the first drops of distillate are observed.
    • Record the finishing temperature at which the distillation of the first component is complete.
    • Compare the observed temperature range against the previously researched literature value range.
  • Container Handling:
    • Once the first distillation phase is finished, carefully remove Container #1. Caution is required as the container will be hot.

Distillation of Toluene (Second Distillate)

  • Transition Phase:
    • Place Container #2 (Toluene) under the receiving end immediately after removing the first container.
    • Continue monitoring the temperature, noting when it begins to rise again.
  • Collection Protocol:
    • Once the vapor temperature reaches a threshold above approximately $95\,^{\circ}C$, monitor for the first drops appearing in Container #2.
  • The second distillate is identified as "pure" toluene separated from the mixture.
  • Data Recording for Toluene:
    • Record the starting temperature when the second distillate begins to collect.
    • Record the finishing temperature when the second distillate completes its distillation process.
    • Compare the observed temperature range for this phase against the researched literature value range.
  • Container Handling:
    • Remove Container #2 carefully upon completion, noting that it will be hot.

Post-Distillation Cleanup and Measurement

  • Cooling and Disassembly:
    • Turn off the hotplate once both distillates have been successfully collected.
    • Allow the entire apparatus to cool significantly.
    • Do not begin disassembling the apparatus until it is cool enough to touch safely.
  • Volume Measurements:
    • Measure the exact volume of the collected "pure" cyclohexane distillate and record the value.
    • Measure the exact volume of the collected "pure" toluene distillate and record the value.
  • Waste Disposal:
    • All liquid waste must be discarded in the designated liquid waste container.

Quantitative Analysis and Calculations

  • Mass Calculations:
    • Calculate and record the mass in grams ($g$) for the collected cyclohexane.
    • Calculate and record the mass in grams ($g$) for the collected toluene.
  • Concentration Calculation:
    • Calculate and record the percent by mass of cyclohexane in the original mixture.
  • Reference Properties (from notes):
    • Density of Cyclohexane is approximately $0.879\,g\,cm^{-3}$ (derived from transcript notation "cyclo 0.879").