The following questions are referring to a solution of toluene and ethyl acetate

Question

The following questions are referring to a solution of toluene and ethyl acetate. The solution was made by mixing 1.0 mL of ethyl acetate with 2.0 mL of toluene. Information about each chemical is provided below: Calculate the mole fraction of toluene in the toluene-ethyl acetate solution. What is the total vapor pressure above the toluene-ethyl acetate solution at 25 degree C? Calculate the mole fraction of toluene in the vapor (at 25 degree C) above the toluene-ethyl acetate solution. Which compound (toluene or ethyl acetate) do you expect to elute from the GC first? The GC column separates by boiling point only.

Explanation / Answer

Mole fraction of toluene=moles of toluene/(moles of toluene+moles of ethyl acetate)

1.

Calculate moles of toluene-

Density=mass/volume

Or,mass=volume x density

Mass of toluene=1.0 mL x 0.867 g/mL

=0.867 g

Moles of toluene=mass of toluene/molar mass of toluene

=0.867/92.14

=0.00940 moles

2.

Calculate moles of ethyl acetate-

Density=mass/volume

Or, mass=volume x density

Mass of ethyl acetate=2.0mL x 0.897

=1.794 g

Moles of ethyl acetate=mass of ethyl acetate/molar mass of ethyl acetate

=1.794/88.11

=0.02036 moles

3.

Calculate mole fraction

Mole fraction of toluene=moles of toluene/(moles of toluene+moles of ethyl acetate)

=0.00940/(0.00940+0.02036)

=0.00940/0.02976

=0.315860

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