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ABSTRACT: This experiment attempted to determine the relationship between vapor pressure and the composition of the solutions of cyclohexane and ethyl acetate at various concentrations. This was achieved through an experimental analysis using the distillation method collecting residual (liquid) and distillate (vapor) sample where their refractive indicies were measured using a refractometer. Through analysis and various calculations this mixture showed to have a negative deviation from the Raoult’s law, resulting in a relatively high boiling point and an azeotrope. INTRODUCTION
The equilibrium between a liquid and vapor in a closed environment at constant temperature and pressure allows one to define the chemical potential of the liquid in terms of the chemical potential of the vapor. If the vapor is ideal, the chemical potential of the pure liquid is defined as: µL= µV°T,p°+RTln(pp°)(1)
where µoV(T, p°) is the chemical potential of the gas in the standard state (p°= 1 bar at the specified temperature, T) and p is the pressure of the vapor above the liquid.
On the first day of the experiment, a calibration curve was constructed after properly preparing various mixtures using cyclohexane and ethyl acetate, as seen in Scheme 1, and reading each solutions’ refractive indicies. After each result was recorded, the data was corrected using Eq. 1 to calculate the refractive indicies at 20 ˚C and plotting the values on excel against the mole fractions of each mixture creating Fig. 1.
An equation was then developed through the fit of the curve where it was later used to determine the mole fraction of cyclohexane with the data collected on the second day,...