Determination of the %Ethanol Present in Alcoholic Beverages
Department of Chemistry, University of Santo Tomas, Manila, Philippines
Given a 25.0 mL commercial alcoholic beverage, the group is expected to be able to compute for its alcohol content with the use of their background and recently-taught knowledge of the process of distillation, which is the technique that is to be applied for the experiment .Knowing ethanol’s, which is the chemical present in all alcoholic drinks, boiling point as 78%, the students are to collect the distilled and separated ethanol into a test tube with a marker indicating that it contains 1.0 mL of the sample from the distillation set-up. The collected distillate is then subjected to a flammability test in order to know in which volume the ethanol content is high (in which most of the groups’ results are in between 11.0 – 12.0 mL). The collected data and results are then computed for the percent ethanol, in which in this group appeared to be as 48%.
Ethanol is a primary alcohol; it is a compound that is a clear liquid, commonly referred to as “alcohol,” found in alcoholic beverages. Ethanol (CH3CH2OH), also referred to as grain alcohol, is obtained from the fermentation of grains or fruits, a process that has been widely used for thousands of years. Industrially, ethanol is prepared via the acid-catalyzed hydration of ethylene. All alcoholic drinks contain a certain amount of ethanol, which is the safest form of alcohol that is to be ingested by human. Though regarded as ‘somewhat’ safe, still, alcohol consumption is to be always observed in order to not have unwanted effects. Alcohol is prepared by fermentation, in which microorganisms assist in chemical breakdown of a substance. In production of alcoholic beverage, addition of yeast to previously prepared mixture is an example of fermentation. The yeast mixed with sugar turns it into alcohol during the process that last from several days or even years, brewers of such drinks have proven that the longer the fermentation is, the greater the taste of the drink will be.
Distillation is the general technique used for removing a solvent, purifying a liquid, or separating the components of a liquid mixture. In a distillation, a liquid (mixture) is heated to the temperature at which it changes to a vapor. The vapor is then cooled, and thus liquefied, in another part of the apparatus (the condenser). Distillation involves having knowledge of the substance’s boiling point since it involves heating it in order to separate it. In distillation, the vapor temperature which is in equilibrium with the boiling liquid is the temperature being recorded rather than the distilling flask . Knowing the boiling point of the compounds being subjected to the process of distillation is a critical part since you subject it to heat and allowing it to boil then you are expected to collect the correct vapor, which then undergoes condensation in order to return to its liquid phase, from the mixture being separated apart. Boiling is not a necessary requirement for distillation, but it certainly accelerates the process. What is boiling? A liquid is boiling when the vapor pressure of the liquid equals that of the atmosphere giving the liquid the maximum rate of escape into the vapor phase. If a liquid has a low boiling point, its intermolecular forces are low and less energy is needed for molecules to escape into the vapor phase at their maximum rate. So if a liquid has a low boiling point, it has a higher vapor pressure at any temperature, but the maximum rate of escape can be achieved at a relatively low temperature. It is important to realize that like other phase changes, boiling is an equilibrium process. When a liquid is boiling the escaping tendency of the liquid into the gas phase equals that of the gas into the liquid phase.
There are two types of distillation set-ups; the simple and the fractional.
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Ault, A. (1983). Techniques and Experiments for Organic Chemistry (4th Edition). Newton, Massachusetts: Allyn & Bacon, Inc.
Klein, D. (2012). Organic Chemistry. Danvers, MA: John Wiley & Sons, Inc.
Laboratory Manual for Organic Chemistry
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