Experiment O03 Chemical properties of ethanol
Chemicals:
A. Universal indicator, (3 drops)
Ethanol. (1 cm3)
B. 1 M H2SO4, (10cm3)
Solid sodium dichromate(VI), Na2Cr2O7, (3 g)
Anti-bumping granules, (2)
Ethanol, (5 cm3)
Fehling's solution 1, (1 cm3)
Fehling's solution 2, (1 cm3)
2 M NaOH, (1 drop)
0.05 M AgNO3, (5 cm3)
2 M ammonia solution. (~1 cm3)
C. 1 M H2SO4, (10 cm3)
Solid sodium dichromate(VI), Na2Cr2O7, (5g)
Concentrated H2SO4, (2 cm3)
Anti-bumping granules, (3)
Ethanol, (1 cm3)
Universal indicator papers,
Anhydrous sodium carbonate. Na2CO3, (1g)
D. Ethanol, (5 drops)
Iodine solution (10% I2 in KI solution), (1 cm3)
2 M NaOH. (~10 cm3)
E. Ethanol, (1 cm3)
Sodium. (small pieces under oil)
F. Ethanol, (2 cm3)
Glacial ethanoic acid, (1 cm3)
Conc.H2SO4, (3 drops)
1 M Na2CO3. (10 cm3)
G. Ethanol, (2 cm3)
Pumice stone, (4-8 mesh)
Bromine water, (2 drops)
Acidified 0.01 M KMnO4. (2 drops)
P.1
Experiment O03 Chemical properties of ethanol
Apparatus:
A. Safety spectacles,
Test-tube.
B. Safety spectacles,
Protective gloves,
Ground-glass-joint apparatus in fig.1
10 cm3 measuring cylinder,
Spatula and 3 teat-pipettes,
Small funnel, wide stem.
C. Safety spectacles,
Protective gloves,
Ground-glass-joint apparatus in fig.1
Measuring cylinder, 10 cm3,
Spatula and teat-pipette,
Small funnel, wide stem.
D. Safety spectacles,
2 teat-pipettes,.
E. Safety spectacles,
Forceps,
Filter paper,
Splint,
Watch glass.
F. Safety spectacles,
Teat-pipette (1).
G. Safety spectacles,
3 test-tubes with corks,
Ceramic wool,
Teat pipette (1),
Delivery tubes and bungs as in Fig.3
Water trough.
P.2
Experiment O03 Chemical properties of ethanol
Aim
The purpose of this experiment is to study some of the reaction of ethanol, a typical primary alcohol.
Introduction
The reactions to be investigated, with approximate timesrequired, are:
A. Solubility in water Individual 5 minutes
B. Mild oxidation Group 1&2 30 minutes
C. Further oxidation Group 3&440 minutes
D. Triiodomethane reaction Individual5 minutes
E. Reaction with sodium Individual5 minutes
F. Esterification Individual5 minutes
G. Dehydration Group 530 minutes
Your teacher may want you to divide up the experiment amonga group, with each member reporting back on two parts.
You will use Fehling's solution in some of your tests.
This solution contains a blue copper(II) compound which,in the presence of a reducing agent, changes to a red copper(I) compound.
Cu2+ + e- Cu+ Cu2O
Blue Red
You will also use an ammoniacal solution of silver oxide(Tollen's reagent) which, in the presence of a reducing agent, produces a 'silver mirror' (and/or a grey ppt):
Ag+ + e- Ag(s) Silver mirror
Each of these tests confirms the presence of a reducing agent.
Hazard warning
1. Ethanol is very flammable.
2. Bromine and glacial ethanoic acid have dangerousfumes and burn the skin.
3. Concentrated sulphuric acid is very corrosive and reacts violently with water.
4. Tollens' reagent for the silver mirror test becomes explosive if dry.
5. Sodium is extremely dangerous.
6. Sodium dichromate(VI) is a powerful oxidant and can damage the skin.
P.3
Experiment O03 Chemical properties of ethanol
Procedure:
A. Solubility in water
1. Pour about 1 cm3 of distilled water into a test-tube,add a few drops of universal indicator and shake gently.
2. Add about 1 cm3 of ethanol and shake the mixture. Note,in the Results Table, whether the addition of ethanol has any effect on the colour of universal indicator. (Your distilled water may be weakly acidicdue to the absorption of atmospheric carbon dioxide.)
B. Mild oxidation
1. Into a pear-shaped flask, pour 10 cm3 of 1 M sulphuric acid. Using a small wide-stemmed funnel, add 3.0 g ofsodium dichromate(VI) and 2-3 anti-bumping granules.
2.Swirl the flask gently until all the sodium dichromate(VI) has dissolved.
3.Slowly add 5 cm3 of ethanol and swirl to mix.
4.Set up the apparatus shown in figure 1.Ensure that water enters the condenser from the bottom and leaves at the top.
Fig. 1 Distillation
5.Heat very gently until 2-3 cm3 of liquid has distilledover.
6.Keep the distillate and test it in the following ways:
(a)Smell cautiously (compare with ethanol).
(b)Transfer about 1 cm3 of the distillate to atest-tube. Add about 1 cm3 of Fehling's solution 1followed by 1 cm3 of Fehling's solution 2. Boilgently. Note your observations in the Results Table.
(c) Pour about 5 cm3 of 0.05 M silver nitrate solution into a boiling-tube. Add one drop of sodium hydroxide solution. Drop by drop, add aqueousammonia until the precipitate disappears. Add 2-3drops of the distillate and warm the tube in abeaker containing hot water. Note your observations.(This is called the 'silver mirror test' orthe 'Tollens test')
(Do not keep this solution -- It becomes explosiveon evaporation.)
P.4
Experiment O03 Chemical properties of ethanol
C.Further oxidation
1. Into a pear-shaped flask, pour 10 cm3 of 1M sulphuricacid. Through a wide-stemmed funnel add 5 g of sodiumdichromate(VI) and 2 or 3 anti-bumping granules.
2. Swirl the flask gently until all the sodium dichromate(VI) has dissolved.
3. With care, add 2 cm3 concentrated sulphuric acid.
4. Cool the flask under a running tap.
5. Set up the apparatus shown in figure 2,(preferably in a fumecupboard.)
Fig. 2 Heating under reflux
6. Drop by drop, add 1 cm3 of ethanol down the condenser.
7. Boil gently under reflux for 20 minutes. (While youare waiting you could do reactions D, E and F.)
8. Rearrange your equipment so it is set up as in Figure 1above.
9. Distil 2-3 cm3 of liquid.
10. Test the distillate as follows, and note yor observations.
(a) Smell cautiously (compare with ethanol).
(b) Add a drop to moistened universal indicator paper,
(c) Add a few drops to about 1 g of solid sodium carbonate.
P.5
Experiment O03 Chemical properties of ethanol
D. Triiodomethane (iodoform) reaction
1. In a test-tube, mix 5 drops of ethanol and 1 cm3 ofiodine solution.
2. Drop by drop, add 2 M sodium hydroxide solution untilthe brown colour almost disappears. If you observe noother change, warm the tube in a beaker of hot water.
3. Note what happens and smell the product cautiously.
E. Reaction with sodium(Work at a fume-cupboard, withyour teacher present)
1. Pour about 1 cm3 of ethanol into a test-tube.
2. Using forceps, pick up a 1 mm cube of sodium andremove the oil from its surface on filter paper.Drop the sodium into the ethanol.
3. With the front of the fume cupboard pulled down as far as is practically possible, test the gas witha lighted splint.
4. Pour a little of the product from step 2 on to awatch-glass, leave in the fume cupboard and allowto evaporate. Describe what remains.
F. Esterfication
1. Into a test-tube, pour 2 cm3 of ethanol and 1 cm3 of glacial ethanoic acid.
2. With care, add 2-3 drops of concentrated sulphuricacid.
3. Warm gently for a few minutes but do not boil.
4. Pour the product carefully into a beaker containing10 cm3 of 1 M sodium carbonatesolution.Stir and smell.Note your observations.
P.6
Experiment O03 Chemical properties of ethanol
G. Dehydration
1. Push enough ceramic wool down to the bottom of thetest-tube to fill it to a depth of 2 cm.
2. Using a pipette, drop 2 cm3 of ethanol onto the ceramicwool and allow to soak into the wool.
3. Fill up the rest of the test-tube with the pumice stone.
4. Sep up the apparatus shown in figure 3, in the fume-cupboard, making sure clamp(A) is at the open endof the test-tube.
Figure 3
5. Holding the Bunsen burner in your hand, heat the pumicestone quite strongly (without melting the tube!) and occasionally heat the ethanol gently to drive thevapour over the hot pumice.
6. Allow the first bubbles to escape (this is displacedair) before collecting the gas over water.
7. Collect a tube of gas (two if possible), cork andplace in a rack.
8. Test separte tubes of gas as follows and note yourobservations.
(a) Shake with 1-2 drops of bromine water.
(b) Shake with 1-2 drops of acidified potassiumpermanganate solution.
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Experiment O03 Chemical properties of ethanol
Name:
Seat No.:
Date:
Grade:
Results Table (Reactions of ethanol)
Property/Reaction / ObservationsA
/ a. Solubility in waterb. pH of solution. / a.
b.
B / Mild oxidation:
a. Smell.
b. Fehling'ssolution.
c. Silver mirrortest. / a.
b.
c.
C / Further oxidation:
a. Smell.
b. Universalindicator paper.
c. Sodium carbonate. / a.
b.
c.
D / Triiodomethane reaction
E / Reaction withsodium
F
/ EsterificationG / Dehydration
a. Bromine water
b. Acidified potassiumpermanganate
solution / a.
b.
Questions
1. Which of the reactions of ethanol produced a reducingagent? What is the reducing agent?
2. Which of the reactions of ethanol produced an acidiccompound? The smell should give you a clue as to whatit might be. What is the acidic compound?
3.What conditions and relative proportions of reactants are used in the oxidation of ethanol to favour theproduction of (a) ethanal, (b) ethanoic acid?
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