Experiment 6: Unknown Binary Mixture
Patricia G.
May 17, 2019
Introduction
Identifying unknown compound is a very important study for chemical scientists. Chemists use
many different techniques in identifying unknow
...
Experiment 6: Unknown Binary Mixture
Patricia G.
May 17, 2019
Introduction
Identifying unknown compound is a very important study for chemical scientists. Chemists use
many different techniques in identifying unknown compounds that are used in many different
sectors of studies. Unknown compounds are constantly identified in the pharmaceutical
industries, forensic departments, healthcare and many more. Several tests are performed to
ensure that there is a qualitative analysis in identifying the unknown compounds. In this
experiment, an unknown binary mixture was separated and purified, and the compounds of the
mixture were determined.
The first step performed in identifying the binary compound is to do the preliminary examination
of the unknown. The state, odor, and color of the mixture is observed and noted. Next, different
technique is performed to separate the unknown binary mixture. Liquid-liquid mixtures are
separated via acid base extraction, while solid-liquid mixtures are separated via fractional or
simple distillation and crystallization. To obtain the pure solid compound of a binary mixture, the
solid is crystalized by using an ideal solvent that gives the borderline solubility of the solid. In
crystallization of the solid, the solid compound of the binary mixture dissolves in the ideal hot
solvent and precipitates in ice bath. The pure solid is finally collected by vacuum filtration and
the melting point of the pure solid compound is obtained. The boiling point of pure liquid was
obtained by performing fractional distillation. The boiling temperature of a pure liquid
compound in distillation can be obtained when its vapor pressure is equal to the vapor pressure
of the atmosphere. For a pure liquid the boiling temperature should remain constant for the
duration of the distillation.
Nuclear magnetic resonance (NMR) spectroscopy and infrared (IR) spectroscopy are the major
spectroscopic techniques used by organic chemists to identify functional groups in molecules and
to determine the structure of a compound. It is essential to analyze qualitative tests for organic
functional groups to gain insight of the functional groups present in the unknown compounds. A
series of solubility tests were also conducted to detect the presence of an acid, base or neutral
substance in the pure compounds. Lastly, a derivative is formed for each unknown to verify that
the correct identity is determined. A derivative is a new compound that forms from the unknown
however, with a new functional group. The similarity between the melting point of the purified
derivative to the literature melting point of the derivative proves successful identification of the
unknown compound of the binary mixture.
Observation and Results
Part A: Preliminary Examination
Unknown 94 is a liquid-solid binary mixture with a very strong odor. The solid is white in color
and the liquid is clear in color. The compound has low volatility; it does not vaporize at room
temperature.
Part B: Separation & Purification
Simple distillation was used to separate the pure liquid from impure liquid. While, the pure solid
was obtained by crystalizing the impure solid. To find the pure liquid, a simple distillation
apparatus was set up with the unknown liquid in distilling flask. The first drop of distillate was
obtained at 81 , and then most of the pure liquid was obtained at 113 where the temperature ℃ ℃
reached its maximum point indicating the boiling point of the unknown liquid. The last few
drops were collected in a separate beaker when the temperature started to decrease. The leftover
liquid in distilling flask when cooled to room temperature became solid precipitate, which
suggested that all impurities were separated from unknown liquid.
The unknown solid was crystalized with the correct solvent to obtain the pure solid. In order to
determine the correct solvent for recrystallizing, multiple solvents were tested, however only hot
methanol completely dissolved the unknown solid. After determining the correct solvent for the
unknown, all the solid were dissolved in hot methanol and precipitated in ice bath. The final
product of the pure solid was obtained by vacuum filtrating the precipitate. The pure solid had a
crystal-like appearance with a strong odor. The melting point od the pure solid is 36-39 . ℃
- Boiling point of pure Liquid: 113℃
- Melting point of pure solid: 36-39 . ℃
Pact C: Solubility Tests
Solubility Test for Unknown S
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