Ochem Lab 2 - Lab report PDF

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Nana Boateng Lab Partner: Morgan Ballard 6.11.2018, CHEM 3105 – 301 TA: Sophia Sagala Experiment 2: Solvent Extraction Purpose The purpose of this experiment is to separate a mixture of a hydrocarbon and a carboxylic acid. As well as observing the difference between water solubility with a neutral carboxylic acid and its conjugate base, to separate it from a neutral hydrocarbon. Reaction and Physical Properties Table

Compound Naphthalene Biphenyl Benzoic acid oChlorobenzoi c Acid Diethyl ether

MW (g/mol) 128.17 154.21 122.12 156.57

Amount

74.12

40 mL

-

mp(°C)

bp(°C)

78-80 68-70 120-122 140-142

-

-

35

Density (g/mL) -

0.7184

2M NaOH 6 N HCl Sat’d NaCl

-

5 mL 2 mL 10 mL

-

-

-

Safety Ether Risk Statements:  Volatile and Flammable Safety Statements:  In case of contact with eyes, rinse immediately with plenty of water and seek medical advice  Wear suitable protective clothing Sodium hydroxide Risk Statements:  Causes burns and quickly burns skin Safety Statements:  In case of contact with eyes, rinse immediately with plenty of water and seek medical advice  Wear suitable protective clothing, gloves and eye/face protection  In case of accident or if you feel unwell, seek medical advice immediately (show label where possible)  Avoid release to the environment. Refer to special instructions safety data sheet Naphthalene Risk Statements:  Flammable  Can cause Liver and Kidney damage Safety Statements:  In case of contact with eyes, rinse immediately flush eyes with plenty of water for 15 minutes and seek medical advice  In case of inhalation, expose self to fresh air and seek medical advice  In case of contact with skin, rinse skin immediately plenty of water and soap for 15 minutes while removing clothes and seek medical attention. Biphenyl Risk Statements:  Possible sensitizer  Can cause Liver and Kidney damage Safety Statements:  In case of contact with eyes, rinse immediately flush eyes with plenty of water for 15 minutes and seek medical advice

 

In case of inhalation, expose self to fresh air and seek medical advice In case of contact with skin, rinse skin immediately plenty of water and soap for 15 minutes while removing clothes and seek medical attention.

Benzoic Acid Risk Statements:  Respiratory tract irritant  Can cause serve eye irritation  Can cause skin irritation  Safety Statements:  In case of contact with eyes, rinse immediately flush eyes with plenty of water for 15 minutes and seek medical advice  In case of inhalation, expose self to fresh air and seek medical advice  In case of contact with skin, rinse skin immediately plenty of water and soap for 15 minutes while removing clothes and seek medical attention. Procedure 1) Reagents and Equipment a) Add 40 mL of 2M NaOH in an Erlenmeyer Flask then cool in an ice bath. b) Obtain .50g of an unknown composition and record the sample number. c) Weigh sample using an analytical balance, and save a few milligrams for a melting point in next experiment. d) Transfer the remaining of the sample into the seperatory funnel (with the stopcock closed) then add about 30 mL of ether and swirl to dissolve the solid. 2) Separation of the Acidic Component: a) Add NaOH to the ether 5-10 mL at a time. b) Use pH paper to check that the aqueous layer is basic. If not, add more NaOH until the layer is basic. c) Remove the stopper and drain the aqueous layer into an Erlenmeyer flask labeled “Basic extract”. d) Wash the organic layer by adding 10 mL of distilled water to the separatory funnel, shaking, venting, and draining the water into the basic extract. 3) Separation of the Hydrocarbon Component: a) Transfer the ether layer into another Erlenmeyer flask labeled “ether wash”.

b) Return the basic extract into the separatory funnel then wash it by adding 10 mL of fresh ether and shake, vent, and drain the aqueous layer into the basic extract. c) Add the contents of the ether wash flask into the separatory funnel, then add about 10 mL of saturated aqueous NaCl to the ether wash. Shake and vent the combined ether layers. d) Drain the water layer into the basic extract flask, and drain the ether layer into the ether wash flask. e) To remove the small traces of water from the ether wash add a small amount of anhydrous magnesium sulfate to the ether. 4) Isolation of the Acidic Component: a) Add 8mL of 6N HCl to recover acid from the basic extract. Check that the final pH is 1-2, if not add more HCl until the aqueous layer remains acidic. b) A voluminous precipitate should form – collect this solid using a vacuum filtration, using a Hirsch funnel. c) Wash the flask with 15 mL or less of cold distilled water to ensure that all the crystals get onto the funnel and that any water soluble material is washed off the filtrate. d) Save the sample for next lab period. e) Allow the sample to dry on a piece of filter paper in your glassware drawer. The left over aqueous phase can be washed down the sink. 5) Isolation of the Hydrocarbon Component: a) Pour the ether through a conical filter to separate it from the magnesium sulfate. b) Evaporate the ether by blowing a gentle stream of air over it, in the hood. c) Store the remaining solid hydrocarbon in a covered shell vial until next lab period. ______________________________________________________________________________ Data/Observation We used Unknown #6 in this experiment. The weight of the sample was 0.500 grams. When the basic and ether components were added into the separatory funnel the basic extract was always on the bottom due to the density of the aqueous solution. The litmus paper confirmed the bottom layer was basic. Adding HCl to the basic extract caused cloudy precipitation. The solid from the precipitate was filtered and left in the lab to be used for next week’s experiment. The solids that were produced were both white in color. Calculations/Results N/A Conclusion/Discussion

This lab was very successful due to the fact that we were able to separate components based on water solubility, leaving us with two solids at the end of lab. When adding bases into the ether solution the organic acid molecule in the mixture was removed and was soluble in the aqueous layer of the mixture due to the presence of oxygen and sodium ions. Adding HCl into the basic extract resulted in precipitation that means that HCl is more acidic then an organic acid. The precipitate for both the basic and the ether will be tested for melting point in Experiment 3. Both the solid compounds were isolated and will be kept for the next experiment. Post Lab Questions: 1. Ether (MW = 46) evaporates much faster than water (MW = 18), yet ether’s molecular weight is about 2.5 times than that of water. Explain. Although the ether sample is heavier than the water sample, the molecular weight does not necessarily determine the boiling point of a molecule. The molecular structure is more of a determining factor in finding and explaining boiling point. The structure of water has a polar covalent bond as well as stronger intermolecular forces, such as hydrogen bonding, then ether. These facts cause water to have a much higher boiling point compared to ether, therefor causing the water solution to evaporate slower. 2. Suggest a way to separate a mixture of these two compounds. Hint: Amines (R-NH2) can act as bases. Answer can be written out or depicted in a flowchart. Due to the fact that amine can act as bases, you have to add in a very strong acid such as HCl causing the ether solution to separate. In order to accomplish this, you must use a separatory funnel as the reaction container, so when the solution separates into two layers one layer would be able to be removed. Of the layers one is aqueous, and the other is organic. Since the amine is a weak base, it can easily be displaced from an HCl solution by a very strong base....