Simple Distillation Of Cyclohexane
Mona Vaidya
02/04/2014
CHE 317
Laboratory Experiment #1: Simple Distillation of Two Volatile Liquids Containing Non-Volatile Impurities
Introduction: Simple distillation is a commonly used method to separate and purify the mixtures of organic liquids into their original components. Mixtures of two miscible liquids with two different boiling points were separated. Therefore, it can be said that the two organic compounds are separated by exploiting the different boiling temperatures of the liquids. Both vaporization and condensation were used in this experiment. The two organic compounds used in this experiment were ethyl benzene and cyclohexane, which have the boiling point of 136°C and 80.74°C, respectively. This experiment resulted …show more content…
in two relatively pure individual components.
Simple distillation is a method to purify and separate organic compounds. To understand distillation, it is significant to address the physical property on which it is based on. This physical property is known as the boiling point of a liquid. Boiling point is defined as the temperature at which the vapor pressure of a liquid is equal to the external pressure. Therefore it can be said that the boiling point of a liquid is directly proportional to the pressure above the liquid. By applying increasing amounts of heat to a boiling point will not increase the temperature of the liquid, it will only cause it to boil faster. Simple distillation consists of evaporating (boiling) a liquid, which result in the vapors to condense and those vapors are then collected.
A mixture consisting of cyclohexane and ethyl benzene is heated up after the apparatus for the simple distillation is set up.
Since cyclohexane has a lower boiling point, it will evaporate and then vaporize around 80°C (cyclohexane boiling point); this organic liquid will be the first to be collected because it is less volatile in comparison to ethyl benzene. The temperature will continuously increase until all of the cyclohexane has been collected. After all of it has been collected, the temperature will either plateau or plummet down. Once this is observed, the heat is increased because it is more volatile; the boiling point of ethyl benzene can be observed and it will be collected in the graduated cylinder. The boiling point for ethyl benzene is 136°C. Once enough volume is collected, the experiment is …show more content…
halted.
Noted Observations: The mixture was a clear and colorless liquid.
Experimental Procedure: First, the simple distillation apparatus was assembled and a 100 mL round-bottomed flask was used for the still pot. The thermometer/ adapter was then removed and the long-stem plastic funnel was used to insert 60 mL of the mixture. The color and clarity were noted. Then, the funnel was removed from the apparatus and the magnetic stirring bar was added in. The thermometer/ adapter was assembled back on. A 100 mL graduated cylinder was placed to collect the drops of liquid from the condenser. The instructor then checked the apparatus before heating. The stirring and heating of the distillation flask was set on “4”. As soon as the liquid boiled and the condensing vapors reached the thermometer bulb, the heat supply was regulated so that there was only one drop that was dripping per second. As soon as the drops began to fall in the receiver, the temperature was recorded from the thermometer. Thereafter, the temperature was recorded every 4 mL. Once there was a second temperature plateau, the heating was discontinued and the flask was allowed to cool down. The distillation was then halted to streamline the exercise to conserve time.
Experimental Data:
Distillate Volume (mL)
Vapor Temperature (°C)
1st Drop
79.5 °C
4 mL
81.5 °C
8 mL
83.5°C
12 mL
84.0°C
16 mL
86.0°C
20 mL
88.5°C
24 mL
90.0°C
28 mL
94.5°C
32 mL
127.0°C
36 mL
132.0°C
40 mL
137°C
44 mL
138°C
Results/Discussion:
Simple distillation was used to purify and identify organic liquid that contained the volatile compounds: cyclohexane and ethyl benzene.
Since simple distillation is a physical process, it separated the two chemicals from the mixture based on how easily they vaporize. As the mixture was heated, the temperature rose until it reached the temperature of the lowest boiling substance in the mixture which was cyclohexane. The temperature at which the first drop was collected was 79.5oC and the distillation of cyclohexane was stopped when the still-head temperature was 94.5oC . Therefore, the boiling range of cyclohexane in this experiment was 79.5oC- 94.5oC.The resultant hot vapor passed through into the condenser and was converted into liquid, which was then collected into a graduated cylinder. During this time, the ethyl benzene remained in its original phase. Since cyclohexane had a lower boiling point, it is considered to be more volatile in comparison to ethyl benzene. After a plateau in temperature was observed, the temperature was increased in order for ethyl benzene to reach its boiling point. The temperature at which ethyl benzene was collected was 127oC and the distillation of ethyl benzene was stopped when the still-head temperature was 138.5oC. The boiling range for ethyl benzene was observed to be in between 127oC-138.5oC. The liquids were collected in increments of 4mL. The first 28mL collected were of cyclohexane and the last 16 mL collected were of ethyl benzene,
thus giving a ratio of 7:4 respectively. The liquid before heating was clear and colorless and the liquid after heating was also clear and colorless. This experiment concludes that the cyclohexane is more volatile in comparison to ethyl benzene; this can be said because cyclohexane has a lower boiling point when compared to ethyl benzene. Since it was observed that the mixture was a clear and colorless liquid before heating and the compounds were the same colorless and clear liquid after heating, it can be said that the mixture was “pure” to start off with. Simple distillation determined the boiling ranges of both substances. Boiling point is a useful physical property to characterize pure compounds. At any given temperature a liquid is in equilibrium with its vapor. This equilibrium is described by the vapor pressure of the liquid. The vapor pressure is the pressure that the molecules at the surface of the liquid exert against the external pressure, which is usually the atmospheric pressure. The vapor pressure is a very sensitive function of temperature. When the vapor pressure of the liquid equals the applied pressure, the liquid boils. Thus, the boiling point of a liquid is the temperature at which the vapor pressure equals the applied pressure. The boiling point of a liquid is a measure of its volatility. The lower the boiling point, the higher the volatility.
Questions:
a. In a short paragraph, describe how simple distillation separates two compounds with different boiling points.
Simple distillation is used to separate two liquids with different boiling points. As the liquid being distilled is heated, the first vapors that will form will be that of the compound with the lower boiling point. Purified compounds will boil and form vapors over a relatively small temperature range. As distillation continues, the concentration of the lowest boiling component will decrease. A plateau in temperature indicates that a pure compound is no longer being distilled. This means that the first compound (with the lower boiling point) is all collected. The heat is then increased in order to reach the boiling point of the second compound. The temperature will continue to increase until the boiling point of the compound is approached. Basically what is happening is that, as the mixture is heated, the temperature rises until it reaches the temperature of the lowest boiling substance in the mixture, while the other compound of the mixture remains in the original phase. The hot vapor passes into a condenser and is converted to the liquid, which is then collected. The second compound of the mixture remains in its original phase until the first volatile substance has all boiled off. Only then does the temperature of the gas phase rises again until it reaches the boiling point of a second component.
b. If the thermometer is placed above the outlet to the condenser, will the temperature measured be correct? If not, will it be higher or lower than the actual vapor temperature?
No, if the thermometer is placed above the outlet to the condenser, the temperature measure would not be correct. If the bulb were placed higher than this position, it would not be in the vapor path and would have a lower temperature in comparison to the actual vapor temperature.
c. What are boiling stones and why are they added?
Boiling stones are unevenly shaped pieces of substances that are added to liquids to make them boil clamlier. They are added to help prevent superheating of the liquid being distilled and they will cause a more controlled boil. This will eliminate the possibility that the liquid in the distillation flask will bump into the condenser.
d. Describe the observations that one would make during the simple distillation of an "impure" substance.
The boiling point of an impure liquid will change and therefore the observation that can be seen is a change in the composition of the liquid.
e. What happens to the still head temperature during the simple distillation of a pure substance.
As vapors of the pure substance rise from the liquid, they move up the apparatus and will therefore increase the temperature of the still head.
f. In a simple distillation, you measure a boiling range that is 110-121 degrees; How pure do you think the liquid sample is? Explain
If the boiling range during a simple distillation is between 110-121 degree, it can be said to be a pure liquid sample. This is because the given range is approximately 10 degree wide and the boiling point lies within the boiling range. Since the boiling point lies within the boiling range, it can be said that the liquid sample is pure.
g. You have just completed a simple distillation and have made observations of the temperature as the distillate is collected. How would you know whether your distillation was successful and that the distillate is reasonably pure?
If the temperatures stabilize and plateau, then it is evident that the simple distillation is completed and was successful. If the temperature of the first liquid plateau’s and does not increase anymore, then it illustrates that the first compound was pure, since it is the only compound with that boiling point. After the temperature is increased, and the boiling point of the second compound is reached, then its purity would be based on if it also plateau’s. If for any reason there is an increase other than to reach the boiling points of the compounds, then it shows that there are impurities. In this experiment, both compounds are considered to be pure because they both gradually increase in temperature until their boiling point is reached and then they both plateau.
02/04/2014
CHE 317
Laboratory Experiment #1: Simple Distillation of Two Volatile Liquids Containing Non-Volatile Impurities
Introduction: Simple distillation is a commonly used method to separate and purify the mixtures of organic liquids into their original components. Mixtures of two miscible liquids with two different boiling points were separated. Therefore, it can be said that the two organic compounds are separated by exploiting the different boiling temperatures of the liquids. Both vaporization and condensation were used in this experiment. The two organic compounds used in this experiment were ethyl benzene and cyclohexane, which have the boiling point of 136°C and 80.74°C, respectively. This experiment resulted …show more content…
in two relatively pure individual components.
Simple distillation is a method to purify and separate organic compounds. To understand distillation, it is significant to address the physical property on which it is based on. This physical property is known as the boiling point of a liquid. Boiling point is defined as the temperature at which the vapor pressure of a liquid is equal to the external pressure. Therefore it can be said that the boiling point of a liquid is directly proportional to the pressure above the liquid. By applying increasing amounts of heat to a boiling point will not increase the temperature of the liquid, it will only cause it to boil faster. Simple distillation consists of evaporating (boiling) a liquid, which result in the vapors to condense and those vapors are then collected.
A mixture consisting of cyclohexane and ethyl benzene is heated up after the apparatus for the simple distillation is set up.
Since cyclohexane has a lower boiling point, it will evaporate and then vaporize around 80°C (cyclohexane boiling point); this organic liquid will be the first to be collected because it is less volatile in comparison to ethyl benzene. The temperature will continuously increase until all of the cyclohexane has been collected. After all of it has been collected, the temperature will either plateau or plummet down. Once this is observed, the heat is increased because it is more volatile; the boiling point of ethyl benzene can be observed and it will be collected in the graduated cylinder. The boiling point for ethyl benzene is 136°C. Once enough volume is collected, the experiment is …show more content…
halted.
Noted Observations: The mixture was a clear and colorless liquid.
Experimental Procedure: First, the simple distillation apparatus was assembled and a 100 mL round-bottomed flask was used for the still pot. The thermometer/ adapter was then removed and the long-stem plastic funnel was used to insert 60 mL of the mixture. The color and clarity were noted. Then, the funnel was removed from the apparatus and the magnetic stirring bar was added in. The thermometer/ adapter was assembled back on. A 100 mL graduated cylinder was placed to collect the drops of liquid from the condenser. The instructor then checked the apparatus before heating. The stirring and heating of the distillation flask was set on “4”. As soon as the liquid boiled and the condensing vapors reached the thermometer bulb, the heat supply was regulated so that there was only one drop that was dripping per second. As soon as the drops began to fall in the receiver, the temperature was recorded from the thermometer. Thereafter, the temperature was recorded every 4 mL. Once there was a second temperature plateau, the heating was discontinued and the flask was allowed to cool down. The distillation was then halted to streamline the exercise to conserve time.
Experimental Data:
Distillate Volume (mL)
Vapor Temperature (°C)
1st Drop
79.5 °C
4 mL
81.5 °C
8 mL
83.5°C
12 mL
84.0°C
16 mL
86.0°C
20 mL
88.5°C
24 mL
90.0°C
28 mL
94.5°C
32 mL
127.0°C
36 mL
132.0°C
40 mL
137°C
44 mL
138°C
Results/Discussion:
Simple distillation was used to purify and identify organic liquid that contained the volatile compounds: cyclohexane and ethyl benzene.
Since simple distillation is a physical process, it separated the two chemicals from the mixture based on how easily they vaporize. As the mixture was heated, the temperature rose until it reached the temperature of the lowest boiling substance in the mixture which was cyclohexane. The temperature at which the first drop was collected was 79.5oC and the distillation of cyclohexane was stopped when the still-head temperature was 94.5oC . Therefore, the boiling range of cyclohexane in this experiment was 79.5oC- 94.5oC.The resultant hot vapor passed through into the condenser and was converted into liquid, which was then collected into a graduated cylinder. During this time, the ethyl benzene remained in its original phase. Since cyclohexane had a lower boiling point, it is considered to be more volatile in comparison to ethyl benzene. After a plateau in temperature was observed, the temperature was increased in order for ethyl benzene to reach its boiling point. The temperature at which ethyl benzene was collected was 127oC and the distillation of ethyl benzene was stopped when the still-head temperature was 138.5oC. The boiling range for ethyl benzene was observed to be in between 127oC-138.5oC. The liquids were collected in increments of 4mL. The first 28mL collected were of cyclohexane and the last 16 mL collected were of ethyl benzene,
thus giving a ratio of 7:4 respectively. The liquid before heating was clear and colorless and the liquid after heating was also clear and colorless. This experiment concludes that the cyclohexane is more volatile in comparison to ethyl benzene; this can be said because cyclohexane has a lower boiling point when compared to ethyl benzene. Since it was observed that the mixture was a clear and colorless liquid before heating and the compounds were the same colorless and clear liquid after heating, it can be said that the mixture was “pure” to start off with. Simple distillation determined the boiling ranges of both substances. Boiling point is a useful physical property to characterize pure compounds. At any given temperature a liquid is in equilibrium with its vapor. This equilibrium is described by the vapor pressure of the liquid. The vapor pressure is the pressure that the molecules at the surface of the liquid exert against the external pressure, which is usually the atmospheric pressure. The vapor pressure is a very sensitive function of temperature. When the vapor pressure of the liquid equals the applied pressure, the liquid boils. Thus, the boiling point of a liquid is the temperature at which the vapor pressure equals the applied pressure. The boiling point of a liquid is a measure of its volatility. The lower the boiling point, the higher the volatility.
Questions:
a. In a short paragraph, describe how simple distillation separates two compounds with different boiling points.
Simple distillation is used to separate two liquids with different boiling points. As the liquid being distilled is heated, the first vapors that will form will be that of the compound with the lower boiling point. Purified compounds will boil and form vapors over a relatively small temperature range. As distillation continues, the concentration of the lowest boiling component will decrease. A plateau in temperature indicates that a pure compound is no longer being distilled. This means that the first compound (with the lower boiling point) is all collected. The heat is then increased in order to reach the boiling point of the second compound. The temperature will continue to increase until the boiling point of the compound is approached. Basically what is happening is that, as the mixture is heated, the temperature rises until it reaches the temperature of the lowest boiling substance in the mixture, while the other compound of the mixture remains in the original phase. The hot vapor passes into a condenser and is converted to the liquid, which is then collected. The second compound of the mixture remains in its original phase until the first volatile substance has all boiled off. Only then does the temperature of the gas phase rises again until it reaches the boiling point of a second component.
b. If the thermometer is placed above the outlet to the condenser, will the temperature measured be correct? If not, will it be higher or lower than the actual vapor temperature?
No, if the thermometer is placed above the outlet to the condenser, the temperature measure would not be correct. If the bulb were placed higher than this position, it would not be in the vapor path and would have a lower temperature in comparison to the actual vapor temperature.
c. What are boiling stones and why are they added?
Boiling stones are unevenly shaped pieces of substances that are added to liquids to make them boil clamlier. They are added to help prevent superheating of the liquid being distilled and they will cause a more controlled boil. This will eliminate the possibility that the liquid in the distillation flask will bump into the condenser.
d. Describe the observations that one would make during the simple distillation of an "impure" substance.
The boiling point of an impure liquid will change and therefore the observation that can be seen is a change in the composition of the liquid.
e. What happens to the still head temperature during the simple distillation of a pure substance.
As vapors of the pure substance rise from the liquid, they move up the apparatus and will therefore increase the temperature of the still head.
f. In a simple distillation, you measure a boiling range that is 110-121 degrees; How pure do you think the liquid sample is? Explain
If the boiling range during a simple distillation is between 110-121 degree, it can be said to be a pure liquid sample. This is because the given range is approximately 10 degree wide and the boiling point lies within the boiling range. Since the boiling point lies within the boiling range, it can be said that the liquid sample is pure.
g. You have just completed a simple distillation and have made observations of the temperature as the distillate is collected. How would you know whether your distillation was successful and that the distillate is reasonably pure?
If the temperatures stabilize and plateau, then it is evident that the simple distillation is completed and was successful. If the temperature of the first liquid plateau’s and does not increase anymore, then it illustrates that the first compound was pure, since it is the only compound with that boiling point. After the temperature is increased, and the boiling point of the second compound is reached, then its purity would be based on if it also plateau’s. If for any reason there is an increase other than to reach the boiling points of the compounds, then it shows that there are impurities. In this experiment, both compounds are considered to be pure because they both gradually increase in temperature until their boiling point is reached and then they both plateau.