Distillation Laboratory Report

Lab report # 2 SIMPLE AND FRACTIONAL DISTILLATION Purpose The purpose of the Simple and Fractional Distillation experiment is to become familiar with the proper techniques used when purifying two volatile mixtures with a difference in boiling point. Introduction Part one: Distillation is a method used to purify a mixture. Once the apparatus is prepared 13 mL of Methanol and water mixture is slowly heated. Since water and methanol have different boiling points the different component of the liquid will evaporate at different times. Simple distillation is used when the difference between the boiling point of a mixture is greater than 40-50˚C. A Bunsen burner is used to heat up the mixture as the temperature rises the compound with the lower boiling point began to vaporized up the condenser and collected at a moderate rate of 0.2 mL per minute. This rate is kept by monitoring the temperature at which the mixture is being boiled. The temperature on thermometer is recorded at every 0.2 mL collected. The temperature is expected to increase gradually until distillate is collected with out no sudden rise in temperature. Part Two: The same method is repeated but this time with a fractional column added to the distillation apparatus. Fractional distillation is used when the difference in boiling point of two substance is close to each other. 13mL of methanol and water mixture is brought to boil and collected at approximately .2mL per minute. The vapor first goes up the column condense and reevaporate many times before fully going through the condenser. By using the Fractional distillation method, better result is expected. There will be a clear change in temperature from one component of the mixture evaporating to another. Methods and materials 1. Table of physical constants • Record to the proper number of significant figures. Chemical Name Chemical structure b.p. (°C) Water 100.0 - 100.1 Methanol 64.7 – 65.0 Results: 1. Data tables: temperature versus volume (Submit the typed data on a separate sheet of paper and attach to your report) Volume Collected ml 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 Simple Temp ˚C 75 76 78 80 79 79 80 81 81 80 81 81 81 81 80 Fractional Temp ˚C 66 66 65 66 66 65 63 64 64 64 64 65 65 64 65 3.2 3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6 6.2 6.4 6.6 6.8 7 7.2 7.4 7.6 7.8 8 8.2 8.4 8.6 8.8 9 9.2 9.4 9.6 9.8 10 79 79 82 83 83 84 84 84 84 87 87 88 88 89 91 92 94 94 95 94 93 94 95 96 96 97 98 99 99 101 64 68 68 71 89 88 89 91 93 94 94 95 96 96 96 96 96 96 96 95 Distillation of Methanol and Water Mixture Simple Temp ˚C Fractional Temp ˚C 100 Temperature ˚C 80 60 40 20 0 0.2 1.2 2.2 3.2 4.2 5.2 6.2 Volume Collected (mL) 7.2 8.2 9.2 a. Observed boiling point of water: 89.0-96.0˚C range b. Literature boiling point of water: 100.0-100.1˚C range c. Volume of water collected: 3.0_mL d. Observed boiling point of methanol: 63.0- 68.0˚C range e. Literature boiling point of methanol: 64.7- 65.0˚C range f. Volume of methanol collected: 3.5 mL 3. Were the recovered water and methanol pure? Give at least one reason why (pure or not pure). Yes the recovered water and methanol was pure based on the boiling point data I collected from observing the mixture distillate approximately 0.2 mL per minute. There was a sudden break in the temperature. Discussion and conclusions: The percent yield of distillate that I was able to collect was 53.8% which is not too bad since there was a few mL more of Methanol-Water mixture left in the round bottom Flask. Based on the data collected and the sudden jump in temperature illustrated in the graph; I believe the distillate collected was pure. One reason the distillation could possibly be unsuccessful is because the starting temperature at which the mixture began to distillate was approximately 66˚C which is approximately 2˚ more than the boiling point of methanol. Sources of error 1. Initially heating up the mixture two fast. I was impatient and was eager to see the firs drop of distillate up the condenser. Improvement: Now I know that the fractional column apparatus takes longer to collect distillate than simple fractionation. Source of error 2 The water tube was not fully seated on the condenser and some water spilled out in the hood. Because of this I had to stop the experiment briefly in order to fix the water tube and relight my Bunsen burner. Improvement: Double check my apparatus and make sure everything is set up properly to minimize mishaps. Questions: Provide details proper to the college organic chemistry level. Do research instead of guessing if you do not know. 1. Specify where a simple distillation or a fractional distillation would be more suitable for each of the following purifications. Briefly justify your choice. a. Separating benzene (bp 80 oC) from toluene (bp 111 oC) Fractional distillation since the difference between boiling points is less than 40˚C b. Removing diethyl ether (bp 35 oC) from toluene (bp 111 oC) Simple distillation since the difference in boiling point is greater than 40-50˚ C 2. Examine the boiling point – composition diagram for mixtures of toluene and benzene given in figure 4.3 (page 136 of the textbook 5th ed). a. Find the normal boiling point of benzene and toluene from the graph. BP of Benzene is 80˚C BP of Toluene is 110˚ C b. Assume you are given a mixture of these two liquids of composition 70 mol % toluene and 30 mole % benzene and that it is necessary to effect a fractional distillation that will afford benzene > 99 % purity. What would be the minimum number of theoretical plates required? The minimum number of plates would be 3 c. For the mixture comprised of 50 mol % benzene and 50 mol % toluene, at what temperature will the mixture begin to boil. 92-93˚ C d. When the liquid mixture containing 50 mol % benzene and 50 mol % toluene is heated to its boiling point, what % of benzene and toluene the vapor formed? Approximately 72% Benzene and 28% Toluene e. If the composition in (d) is condensed what would be more enriched compared to the mixture of the 50 mol % benzene and 50 mol % toluene? 88% Benzene and 13% Toluene so Benzene would be more enriched