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Q3. Estimate the “proof” of the first fraction you obtained from the distillation assuming that the density of ethanol solutions are a linear function of ethanol concentration [measured density = x (Ethanol density) + (1-x) (Water density); 100x = %]. The proof of an alcoholic sample is defined as twice the volume percentage. How does your proof value correspond to a commercially available distilled spirit such as vodka which is commonly 80 proof?  Unfermented:               1000 mL           1.056g First Fraction:       80 °C      250mL         1.180g Second Fraction:    94 °C       250mL         1.209g Third Fraction:         97 °C  250mL         1.212g First Fraction Boiling point = 89.3 °C

Q3. Estimate the “proof” of the first fraction you obtained from the distillation assuming that the density of ethanol solutions are a linear function of ethanol concentration [measured density = x (Ethanol density) + (1-x) (Water density); 100x = %]. The proof of an alcoholic sample is defined as twice the volume percentage. How does your proof value correspond to a commercially available distilled spirit such as vodka which is commonly 80 proof?  Unfermented:               1000 mL           1.056g First Fraction:       80 °C      250mL         1.180g Second Fraction:    94 °C       250mL         1.209g Third Fraction:         97 °C  250mL         1.212g First Fraction Boiling point = 89.3 °C

Introduction to Chemical Engineering Thermodynamics
Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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Q3. Estimate the “proof” of the first fraction you obtained from the distillation assuming that the
density of ethanol solutions are a linear function of ethanol concentration [measured density
= x (Ethanol density) + (1-x) (Water density); 100x = %]. The proof of an alcoholic sample
is defined as twice the volume percentage. How does your proof value correspond to a
commercially available distilled spirit such as vodka which is commonly 80 proof? 

Unfermented:               1000 mL           1.056g

First Fraction:       80 °C      250mL         1.180g

Second Fraction:    94 °C       250mL         1.209g

Third Fraction:         97 °C  250mL         1.212g

First Fraction Boiling point = 89.3 °C

One of the earliest organic chemical reactions understood by man is the fermentation of sugar-containing foodstuffs to make alcoholic beverages. The ability to perform this transformation dates back at least 5000 years. In this laboratory we will examine the process of making beer and the process of distillation as a means to concentrate alcohol solutions. Beer is made from grains which contain starch (carbohydrates) and this first process in beer making is soaking (steeping) and heating (mashing) the grains. This breaks down the starch (long chains of connected sugar molecules) into smaller units of sugars (also carbohydrates but smaller units) to give what is called a malt extract. We will start our beer making at this point with a malt extract and water. Malt extract is a thick syrup or powder which is combined with water. The malt extract contains sugar and as a result has a density greater than that of water (dH;O = 1.00 g/cc). This solution is heated to give a hot sugar solution called wort which is then allowed to cool. At this point we will add yeast which will feed on the sugar and convert it to carbon dioxide and ethanol in a closed (oxygen limited) vessel. Over time the yeast will produce CO2 and ethanol until all of the sugar is consumed (usually 4-5 days at room temperature). This will produce a solution which now has some ethanol and no glucose. This solution still has other materials and as a result the density will still be greater than that of water but should show a measurable decrease from the initial wort. In order to make beer from this material you need to add additional CO2 and bottle the resultant solution. The CO2 can be added from a compressed gas tank or by the addition of a small amount of sugar prior to bottling which is converted by the yeast to CO2 in the bottle (note that too much sugar at this point would result in high CO2 pressures and the bottles will burst!). (C6H1206)n (Starch) C6H1206 heat (Glucose) 2CH3CH2OH + 2CO2 (Ethanol) yeast Mankind has made beer this way for a long long time and has found the resultant beverage to be intoxicating due to its ethanol content. The more ethanol present the more intoxicating the beverage. It turns out that there is a limit to how strong beer can be (in other words there is a maximum ethanol concentration) and to form a more concentrated ethanol solution requires additional processing. Since ethanol is more volatile than water then an ethanol solution will have a higher concentration of ethanol in the gas phase than in the bulk solution (following Raoult's Law). As a practical result a stronger ethanol solution can be prepared by heating the beer solution and converting it to a gas followed by collecting this vapor. This process is called distillation and is how distilled spirits (scotch, whiskey, rum, etc.) are prepared. In this laboratory you will observe the conversion of malt extract and water into still beer (beer without carbonation). You will be able to monitor this conversion by measuring the density of the solution before and after the yeast has converted the glucose to ethanol. You will then take a sample of this ethanolic solution and distill it to obtain a more concentrated ethanolic solution. The purity of the distilled materials will be determined by measuring the density of the CHM-251 Rev 2-Mohrig 4E – AU16 Lab 1. Distillation 2/6 samples obtained and determining the boiling point of the solution before and after distillation.
Transcribed Image Text:One of the earliest organic chemical reactions understood by man is the fermentation of sugar-containing foodstuffs to make alcoholic beverages. The ability to perform this transformation dates back at least 5000 years. In this laboratory we will examine the process of making beer and the process of distillation as a means to concentrate alcohol solutions. Beer is made from grains which contain starch (carbohydrates) and this first process in beer making is soaking (steeping) and heating (mashing) the grains. This breaks down the starch (long chains of connected sugar molecules) into smaller units of sugars (also carbohydrates but smaller units) to give what is called a malt extract. We will start our beer making at this point with a malt extract and water. Malt extract is a thick syrup or powder which is combined with water. The malt extract contains sugar and as a result has a density greater than that of water (dH;O = 1.00 g/cc). This solution is heated to give a hot sugar solution called wort which is then allowed to cool. At this point we will add yeast which will feed on the sugar and convert it to carbon dioxide and ethanol in a closed (oxygen limited) vessel. Over time the yeast will produce CO2 and ethanol until all of the sugar is consumed (usually 4-5 days at room temperature). This will produce a solution which now has some ethanol and no glucose. This solution still has other materials and as a result the density will still be greater than that of water but should show a measurable decrease from the initial wort. In order to make beer from this material you need to add additional CO2 and bottle the resultant solution. The CO2 can be added from a compressed gas tank or by the addition of a small amount of sugar prior to bottling which is converted by the yeast to CO2 in the bottle (note that too much sugar at this point would result in high CO2 pressures and the bottles will burst!). (C6H1206)n (Starch) C6H1206 heat (Glucose) 2CH3CH2OH + 2CO2 (Ethanol) yeast Mankind has made beer this way for a long long time and has found the resultant beverage to be intoxicating due to its ethanol content. The more ethanol present the more intoxicating the beverage. It turns out that there is a limit to how strong beer can be (in other words there is a maximum ethanol concentration) and to form a more concentrated ethanol solution requires additional processing. Since ethanol is more volatile than water then an ethanol solution will have a higher concentration of ethanol in the gas phase than in the bulk solution (following Raoult's Law). As a practical result a stronger ethanol solution can be prepared by heating the beer solution and converting it to a gas followed by collecting this vapor. This process is called distillation and is how distilled spirits (scotch, whiskey, rum, etc.) are prepared. In this laboratory you will observe the conversion of malt extract and water into still beer (beer without carbonation). You will be able to monitor this conversion by measuring the density of the solution before and after the yeast has converted the glucose to ethanol. You will then take a sample of this ethanolic solution and distill it to obtain a more concentrated ethanolic solution. The purity of the distilled materials will be determined by measuring the density of the CHM-251 Rev 2-Mohrig 4E – AU16 Lab 1. Distillation 2/6 samples obtained and determining the boiling point of the solution before and after distillation.
procedure where the condensed liquid will fall down into the depression at the bottom of the still head. This will occur until the still is "full" and then any additional condensed liquid will return to the distillation pot. Since the composition of the condensed liquid is expected to change you should remove liquid when the still head is less than half full (you need 150-250 uL for each fraction). If the still head fills completely the ethanol concentration will decrease significantly. You will remove three samples from the still head which will ideally differ in the amount of ethanol present. You will want to position a thermometer at the top of the still head opening in order to record the temperature of the vapor that is being condensed. The temperature should increase over the course of the distillation as the composition of the solution being heated changes. Boiling Point Determinations and the Ultra micro boiling point determination: The boiling point of liquid can be used to identify or confirm the identity of a liquid. Therefore it is an important physical property which can be related to a liquid's purity and/or composition. In this sense it is similar to melting points for solids. If more than one component is present in a mixture then distillation will result in a change of boiling point as the composition of the mixture changes. A fractional distillation will result in boiling points determined for each component if there are enough theoretical plates to completely separate each component. Ona practical level you would use the boiling point as measured during a distillation as an indication as to what compound(s) are being distilled out of the distillation pot. A steady temperature is a good indication that the composition in a distillation is constant. Conversely a temperature rise in a distillation is interpreted to mean a composition change of the vapor (and a temperature decrease normally means that vapor is not actively being removed from the mixture). The boiling point of a pure compound or mixture (solution) can be determined without setting up a distillation apparatus as shown in Figure 12.2. If you heat a liquid sample in a test tube or conical vial and suspend a thermometer over the sample when it is boiling, you can measure the temperature of the vapor (this represents vapor and liquid in equilibrium). This is a good method to use if you have 1 mL or more for measuring the boiling point. An alternative ultramicro scale method which uses much smaller quantities can also be used but requires more technique. In this method you place a small quantity of liquid (10-50 µL) into a sealed capillary tube. Ản open capillary tube or Pasteur pipette is drawn out in a flame to give a thin capilllary (much thinner than the sealed capillary) which is then cut in the middle. The end is then melted in a flame to give a glass ball on the end and the small capillary is then cut to give a 5-10 mm section. This results in a very small cup or bell which has one open end and a glass ball attached to the sealed end. Note that making the bulb is not easy to master. This glass cup or bell is placed into the sealed capillary upside down such that the sealed end is pointing upward. The sealed capillary now has the liquid sample and the inverted cup inside. This capillary is placed into a Melt-temp (Figure 14.2-14.3) or other capillary melting point apparatus. 'The sample is heated until boiling of the sample is evident and the bell has no liquid in it but is filled with vapor. The heating is discontinued and the sample is slowly cooled. You need to observe this bell very carefully at this stage. When you see that liquid enters the bell record the temperature on the thermometer. This is the boiling point of the sample. The reason that this corresponds to the boiling point is that when the sample is heated above the boiling point the liquid in the bell is converted to vapor at one atmosphere. This will also be true above the boiling point because vapor is the physical state of that material at one atmosphere. When the sample is cooled the pressure in the bell remains 1 atmosphere at all temperatures above the boiling point. When the temperature falls below the boiling point the vapor pressure (pressure in the bell) falls below one atmosphere and the surrounding liquid will enter the bell. This pressure change accounts for the CHM-251 Rev 2-Mohrig 4E – AU16 Lab 1. Distillation 5/6 temperature measured when the bell changes from having vapor to having liquid being equated with the normal boiling point. If you miss the temperature this procedure can easily be repeated without adding additional liquid. You should be careful not to heat the sample to high in temperature since high temperatures will result in a loss of liquid from the capillary tube. Figures for Ultramicro Boiling Point: Note: The bell will contain vapor when the temperature is greater than the boiling point. When the temperature decreases below the boiling point liquid will enter the bell. This observable transition occurs at the boiling point. Observe pure ethanol first where the bp is known.
Transcribed Image Text:procedure where the condensed liquid will fall down into the depression at the bottom of the still head. This will occur until the still is "full" and then any additional condensed liquid will return to the distillation pot. Since the composition of the condensed liquid is expected to change you should remove liquid when the still head is less than half full (you need 150-250 uL for each fraction). If the still head fills completely the ethanol concentration will decrease significantly. You will remove three samples from the still head which will ideally differ in the amount of ethanol present. You will want to position a thermometer at the top of the still head opening in order to record the temperature of the vapor that is being condensed. The temperature should increase over the course of the distillation as the composition of the solution being heated changes. Boiling Point Determinations and the Ultra micro boiling point determination: The boiling point of liquid can be used to identify or confirm the identity of a liquid. Therefore it is an important physical property which can be related to a liquid's purity and/or composition. In this sense it is similar to melting points for solids. If more than one component is present in a mixture then distillation will result in a change of boiling point as the composition of the mixture changes. A fractional distillation will result in boiling points determined for each component if there are enough theoretical plates to completely separate each component. Ona practical level you would use the boiling point as measured during a distillation as an indication as to what compound(s) are being distilled out of the distillation pot. A steady temperature is a good indication that the composition in a distillation is constant. Conversely a temperature rise in a distillation is interpreted to mean a composition change of the vapor (and a temperature decrease normally means that vapor is not actively being removed from the mixture). The boiling point of a pure compound or mixture (solution) can be determined without setting up a distillation apparatus as shown in Figure 12.2. If you heat a liquid sample in a test tube or conical vial and suspend a thermometer over the sample when it is boiling, you can measure the temperature of the vapor (this represents vapor and liquid in equilibrium). This is a good method to use if you have 1 mL or more for measuring the boiling point. An alternative ultramicro scale method which uses much smaller quantities can also be used but requires more technique. In this method you place a small quantity of liquid (10-50 µL) into a sealed capillary tube. Ản open capillary tube or Pasteur pipette is drawn out in a flame to give a thin capilllary (much thinner than the sealed capillary) which is then cut in the middle. The end is then melted in a flame to give a glass ball on the end and the small capillary is then cut to give a 5-10 mm section. This results in a very small cup or bell which has one open end and a glass ball attached to the sealed end. Note that making the bulb is not easy to master. This glass cup or bell is placed into the sealed capillary upside down such that the sealed end is pointing upward. The sealed capillary now has the liquid sample and the inverted cup inside. This capillary is placed into a Melt-temp (Figure 14.2-14.3) or other capillary melting point apparatus. 'The sample is heated until boiling of the sample is evident and the bell has no liquid in it but is filled with vapor. The heating is discontinued and the sample is slowly cooled. You need to observe this bell very carefully at this stage. When you see that liquid enters the bell record the temperature on the thermometer. This is the boiling point of the sample. The reason that this corresponds to the boiling point is that when the sample is heated above the boiling point the liquid in the bell is converted to vapor at one atmosphere. This will also be true above the boiling point because vapor is the physical state of that material at one atmosphere. When the sample is cooled the pressure in the bell remains 1 atmosphere at all temperatures above the boiling point. When the temperature falls below the boiling point the vapor pressure (pressure in the bell) falls below one atmosphere and the surrounding liquid will enter the bell. This pressure change accounts for the CHM-251 Rev 2-Mohrig 4E – AU16 Lab 1. Distillation 5/6 temperature measured when the bell changes from having vapor to having liquid being equated with the normal boiling point. If you miss the temperature this procedure can easily be repeated without adding additional liquid. You should be careful not to heat the sample to high in temperature since high temperatures will result in a loss of liquid from the capillary tube. Figures for Ultramicro Boiling Point: Note: The bell will contain vapor when the temperature is greater than the boiling point. When the temperature decreases below the boiling point liquid will enter the bell. This observable transition occurs at the boiling point. Observe pure ethanol first where the bp is known.
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