Experiment 6: Simple and Fractional Distillation, Lab Reports of Chemistry

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Experiment 6Simple and Fractional Distillation

Vapor Pressure vs Temperature of Water^0 20 40 60 80 100 120 Temperature, °C

140 Vapor Pressure vs Temperature of Water (^250 20015010050) Vapor Pressure (kPa) 0 0 20 40 60 80 Temperature, °C Vapor Pressure vs Temperature of Water (^25020015010050) Vapor Pressure (kPa) 0 100 120 1400 20 40 60 80 100 120 140 Temperature, °C (^25020015010050) Vapor Pressure (kPa)^0

ΔH^ is the energy necessary to vaporize a mole of a pure substancevap^ A^ liq^ A^ B^ vap^ vap A ΔH^ vapB^ ΔH^ vap B^ liq

Ιf mixing liq A and liq B and mixing gas A and gas B results inno heat of mixing in both the liquid and gas phase, the systemis considered to be ideal Then:o P=^ χP;^ PA obs^ A^ AB obs

o= χP BB where PA obs;^ Pis the observed vapor pressure in theB obs^ mixture; χχis the mole fraction of A, B, ...A;^ B^

χ= n/ (n+n)A^ AA^ B^ χ= n/ (n+n)B^ BA^ B oo and P;^ Pare the vapor pressures of pure A and BAB^

At what temperature will a 1:1 molar mixture of cyclohexane-methylcyclohexane boil? P= P+ PT^ A obs^ B obsoo P=^ χP+^ χPT obs^ AA^ BB^ χ=^ χ= 0.5A^ B^ 1 Atm = 101 kPa

T/K^ P/ kPa^ P/ kPa^ CM

T/K^ P/ kPa^ P/ kPaCM

T/K^ P/ kPa^ PC

At what temperature will this ratio of C/M distill? T/K^ C /kPa^ M /kPa 360 121.3^ 66.9 =(1.8/1.8+1)∗121.3 + 1/(1.8+1)∗66.9 = 77.8+23.8 = 101^ Summary^ First theoretical plate ratio 1.8/1; BP 362 K^ Second theoretical plate ~77.8/23.8 = 3.26; BP 360 K

An apparatus for fractional distillation5 theoretical plates can be identified

A look at a schematic diagram of a gas chromatograph:

nstrumental componentsarrier gas^ he carrier gas must be chemically inert. Commonly used gases include nitrogen, helium,rgon, and carbon dioxide. The choice of carrier gas is often dependant upon the type ofetector which is used. The carrier gas system also contains a molecular sieve to removeater and other impurities.^ ample injection port^ or optimum column efficiency, sample sizes should be small and should be introducednto the column as a "plug" of vapor. The most common injection method is where aicrosyringe is used to inject sample through a rubber septum into a heated port at theead of the column. SPME is an alternative method for introducing your sample. For^ acked columns, sample size ranges from tenths of a microliter up to 20 microliters. In^ reparative GC, sample sizes as much as a mL can be used in certain cercumstances.apillary columns, on the other hand, need much less sample, typically less than 10

-3^ mL. or capillary GC, split/splitless injection is used.

Columns There are two general types of column,

packed^ and^ capillary. Packed columns contain a finely divided, inert, solid support material (commonly

diatomaceous earth ) coated with liquid stationary phase. Most packed columns are 1.5 - 10m in length and have aninternal diameter of 2 - 6mm. Liquid coatings vary depending on polarity. Most arenon-volatile waxes or organic liquids. Capillary column Fused silica open tubular columns have much thinner walls than the glasscapillary columns, and are given strength by the polyimide coating.These columns are flexible and can be wound into coils. They have theadvantages of physical strength, flexibility and low reactivity.Temperature range of use varies from room temperature to about 300 °C, depending on the coating. Cyclodextrin is bonded in chiral columns.

It is not unusual for a capillary column to have more anefficiency characterized by more than 100,000 theoreticalplates.