Chemistry Lab Manual_2nd Sem 2012-2013.pdf

1

Foundation Academy for Sciences and Technology

FAST

Chemistry Lab Manual

2012-2013

2

TABLE OF CONTENTS

I. Preface …………………………………………………………… 3

II. Proper Laboratory Techniques and Safe Handling ………………. 4

III. Laboratory Safety Rules ………..………………………………… 12

IV. First Aid ……………………………………………………..…… 17

V. Common Laboratory Apparatus and Their Uses .………………… 20

VI. Student’s Activity Marks ………………………………………….. 27

VII. Solubility Test for Organic Compounds ………………………….. 28

VIII. Baeyer’s Test for Unsaturation..…………………………………….. 31

IX. Bromine Test for Unsaturation …………………………………. 33

X. Properties of Arenes (Benzene) ……..…………………………… 35

XI. Lucas’ Test for 10, 20, and 30 Alcohol …..………………………. 37

XII. Classifying Alcohols Using Acidified Potassium Dichromate……. 39

XIII. Properties of Aldehydes and Ketones ………………………….. 42

XIV. Tollen’s Test for Aldehydes ………………………………….. 44

XV Fehling’s Test for Aldehydes ………………………………………… 46

XVI. Iodoform Test for Methyl Ketones …………………………………… 48

XVII. Oxidation of Carbonyl Compounds by Acidified Potassium Dichromate………. 51

XVIII. Oxidation of Carbonyl Compounds Using Fehling’s Solution ………….………. 53

XIX. Fehling’s Test for Carbohydrates ……………………………………. 55

3

PREFACE

This Chemistry Laboratory Manual is designed specifically for the students in the

Foundation Year to be able to equip them with the knowledge and skills in conducting

experiments following the scientific investigations and guidelines. The manual aims to

help the students to have full understanding of the theoretical concepts being introduced

in the class by having them performed related experiments in the laboratory. Proper

Laboratory Techniques are discussed and by understanding these, the level of safety

in the laboratory will be increased. Safety Rules that should be observed in the lab are

also included. A section on First Aids which explains the things that should be done in

case of accidents is also included. Apparatus that are commonly used in the laboratory

as well as their functions are also given in a separate section. Activities included in this

manual are those related to Organic Chemistry such as Solubility Test for Organic

Compounds, Tests for Unsaturated Hydrocarbons, Properties of Arenes or Aromatic

Compounds, Classifying Alcohols, Oxidation of Carbonyl Compounds by Acidified

Potassium Dichromate, Fehling’s Test for Aldehydes , Iodoform Test for MethylKetones,

and Fehling’s Test for Carbohydrates.

The students are expected to benefit from this manual by having them experience the

excitement and fun of performing every experiment in the laboratory. It will surely

improve their learning ability because activities are prepared in parallel with the lessons

they will have in the class.

So learn and have fun!!! Maria Leila S. Basas, Chemistry Lecturer

Mylene Lourdes L. Delmo, Chemistry Laboratory Instructor

4

PROPER

LABORATORY

TECHNIQUES

&

SAFE

HANDLING

5

PROPER LABORATORY

TECHNIQUES & SAFE HANDLING

Working in the chemistry laboratory, you will be handling potentially

dangerous substances and performing unfamiliar tasks. This section provides you with a guide to

the safe laboratory techniques needed in this course. While performing experiments throughout

the year refer back to this section any time you are unsure of proper laboratory techniques.

Read with understanding the procedure of the experiment or activity.

Make sure that you have the proper equipment, and that you know how to use it.

Always read the label on a reagent bottle before using its contents.

Always wear safety goggles when handling corrosive chemicals.

Always wear face masks when handling chemicals emitting unpleasant odor.

Never touch chemicals with your bare hands. Wear gloves to protect your hands.

Never return unused chemicals to their original containers. To avoid waste, do not take

excessive amounts of reagents.

A. Transferring Solid Chemicals

Solid chemicals are generally kept in reagent bottles. Dark-colored (or Amber) reagent bottles

are used to protect some chemicals from bright light. The following are some techniques in

transferring solid chemicals from reagent bottles:

1. Stoppers of reagent bottles should be laid with the flat side on the table to prevent

contamination.

2. Solid chemicals are spooned out from the reagent bottle using a clean and dry spatula. A

dirty spatula will not only contaminate the portion taken but also that which is left in the

bottle.

3. Use a piece of paper to transfer solids to a small-mouthed container, like a test tube.

Practice the technique of transferring solids to a test tube using common table salt in a sample

reagent bottle.

a. Get a piece of clean paper. Fold it lengthwise. Cut it in such a way that it is about 2 cm

longer than the test tube and slightly wider than its diameter.

b. Place the solid chemical you obtained from the reagent bottle with a spatula near the edge

of the paper.

6

c. Hold the test tube in a horizontal position. Slide the paper into the test tube until it

touches the bottle.

d. Incline the test tube and tap the paper gently. In this way, the solid is deposited at the

bottom of the test tube and not along the sides.

B. Transferring Liquid Reagents

Liquid reagents are usually stored in properly labeled reagent bottles. Liquid reagents should be

poured into clean and dry vessels. To avoid contamination, do not pour reagents directly to a

reaction mixture and do not return excess liquid reagents to their bottles after performing an

experiment.

Ways of transferring liquid reagents depend on the type of receiving vessel. The following are

techniques in transferring liquid reagents into different types of glassware:

1. When pouring a liquid reagent into a wide-mouthed container, the neck of the reagent

bottle must touch the rim of the receiving vessel. A glass rod may also be used to prevent

the liquid from running down the outside surface of t he bottle. The glass rod is held

against the lip of the bottle to direct the liquid into the receiving container.

2. Use a glass rod or a funnel when transferring a liquid reagent into a narrow-mouthed

container.

3. If only a small amount of liquid reagent is needed, a pipette or a medicine dropper may

be used. A pipette is a glass tube calibrated to deliver specific volumes of liquids. When

using more than one liquid reagent, use a separate pipette for each reagent, to avoid

contamination.

Practice the techniques of transferring liquid reagents using a reagent bottle filled with water.

a. Transfer a definite volume of water from the reagent bottle into a beaker by pouring.

b. Use a glass rod in transferring water from the reagent bottle into the beaker.

7

c. Use a glass rod or a funnel to transfer a definite volume of water from the reagent bottle

into an Erlenmeyer flask.

d. Using a pipette, get a definite amount of water from the reagent bottle and transfer it to

the beaker.

8

C. Separating a Solid from a Liquid

Sometimes it is necessary to separate a solid from a liquid. The most common method of

separating such a mixture is filtration.

1. Fold a filter paper circle in half and then quarters. Open the folded paper to form a cone, with

one thickness of paper on one side and three thicknesses on the other.

2. Put the paper cone in a filter funnel. Place the funnel in an iron ring clamped to a ring stand.

Moisten the filter paper with a small volume of distilled water, and gently press the paper against

the sides of the funnel to achieve a good fit. (If the correct size of filter paper has been used, the

top edge of the cone will be just below the rim of the filter funnel.)

3. Place a beaker beneath the funnel to collect the filtrate. The tip of the funnel should touch the

inside surface of the beaker and extend about one inch below the rim. Guide flow of liquid with a

glass rod.

4. Decant the liquid from the solid by pouring it down

a glass stirring rod into the funnel. Be careful to keep

the liquid below the top edge of the cone of filter paper

at all times; the liquid must not overflow. Finally, use

distilled water from a wash bottle to wash the solid into

the filter.

5. When the filtration is complete, wash the solid

residue on the filter paper with distilled water to

remove traces of solvent. Dry the solid.

6. If the filtrate contains a dissolved salt, it may be

recovered by evaporation if desired.

9

D. Measuring Mass

In many experiments you are required to determine the mass of a chemical used or produced in a

reaction. An object’s mass is determined by measuring it on a balance. When you determine the

mass of an object, you are comparing its mass with a known mass. In the SI (International

System), the base unit of mass is the kilogram.

1. Check the balance before you start. The balance pan should be empty and clean, and all

masses (or dials) should be set on zero. The balance must be level. Check the bubble level on the

base.

2. Objects to be placed directly on the balance pan must be clean, dry, and at room temperature.

Solid chemicals and liquids must never be put directly on the balance pan. Liquid samples

should be placed in beakers or sealed containers. Solid chemicals can be conveniently placed in

beakers, disposable plastic weighing boats, or on a piece paper.

3. TARE the container before weighing the sample.

4. The balance is a precision instrument that must be handled with care. To avoid damaging it,

always be sure that the balance is in an arrested position when objects are placed on or removed

from the pan.

5. Never move or jar either a balance or the balance table.

6. If you spill a chemical on or near the balance, clean it up immediately.

7. Never attempt to measure an object with a mass greater than the maximum capacity of the

balance.

8. When you are done, return all the masses to zero, and make sure the balance pan is clean.

E. Measuring Volume

Volume measurements are important in many experimental procedures. Sometimes volume

measurements must be accurate; other times they can be approximate. Most volume measures in

the laboratory are made using equipment calibrated in milliliters. Although some beakers have

graduation marks, these marks are designed only for quick, rough estimates of volume.

Accurate volumes must be measured with pipettes, burettes, or volumetric flasks.

10

1. Using a Graduated Cylinder

Half-fill a 100-mL graduated cylinder with water, and set the cylinder on your laboratory bench.

Examine the surface of the water. Notice how the surface curves upward where the water

contacts the cylinder walls. This curved surface is called a meniscus.

A volume measurement is read at the lower meniscus, with your eye at the same level as the

colorless liquid surface. To make the meniscus more visible, you can place your finger or a dark

piece of paper behind and just below the meniscus while making the reading. A volume

measurement is read at the upper meniscus, with your eye at the same level as the colored liquid

surface.

2. Using a Pipette

A pipette is used to accurately measure and deliver volumes of liquids. Two types are in

common use: volumetric pipettes and graduated, or measuring, pipettes.

A volumetric pipette has a single calibration mark and delivers the volume printed on the bulb of

the pipette at the temperature specified.

A graduated pipette has calibrations along the length of the pipette.

Volumes can be measured more accurately with a volumetric pipette than with a graduated

pipette.

11

Practice the techniques of transferring liquid reagents using

pipettes and pipette aids/ filler with water.

1. Place the tip of the pipette below the surface of the liquid

to be dispensed.

CAUTION: Never fill a pipette by applying suction with

your mouth.

2. Put the pipette aid/filler at the end of the pipette. Roll the adjustable thumb wheel down to take

the liquid until the required volume.

3. Now, deliver the liquid in the pipette into the designated receiver. When releasing liquid from

a volumetric pipette, press the valve lever. Let it drain completely by pressing more the valve

lever.

12

LABORATORY

SAFETY

RULES

13

LABORATORY SAFETY RULES

Dress Appropriately

• When working in the laboratory, always wear your buttoned laboratory coat. Do

not wear unbuttoned long sleeves. Take note of loose clothing

or synthetic garment that may be a fire hazard.

• Wear shoes that completely cover your feet to protect them from spilt corrosive,

broken glasswares, or hot liquids. Do not wear open shoes or sandals in the

laboratory.

• Tie back long hair. Take off any jewellery or

accessories, such as bracelets or necklaces,

which may get in the way of your work.

Wear protective glasses or safety goggles when carrying out

experiments involving concentrated chemicals or while

heating chemicals.

• Wear protective gloves especially when handling chemicals.

Don’t Taste or Sniff Chemicals

Never touch, taste, or smell chemicals. Many chemicals are poisonous. If you are

instructed to note the fumes in an experiment, always gently wave your hand over the

opening of a container and direct the fumes toward your nose. Do not inhale directly

from the container. This isn’t a cooking class – don’t taste your experiments!

14

Don't Play Mad Scientist

Don't haphazardly mix chemicals! Pay attention to the order in which chemicals are to

be added to each other and do not deviate from the instructions. Even chemicals that

mix to produce seemingly safe products should be handled carefully. For example,

hydrochloric acid and sodium hydroxide will give you salt water, but the reaction could

break your glassware or splash the reactants onto you if you aren't careful!

Do Not Pipette by Mouth

You say, "But it's only water." Even if it is, how clean do you think that glassware really

is? Learn to use the pipette bulb or automated pipetter. Don't pipette by mouth at home

either. Gasoline and kerosene should be obvious, but people get hospitalized or die

every year, right?

Heating Procedure

When heating a test tube, hold it at an angle of 450 with a test

tube holder and slowly move it back and forth across the flame.

Point the test tube away from yourself and from others.

Never heat chemical that you are not instructed to heat.

Never reach across a flame.

Never leave a lighted burner unattended.

Always use a clamp or tongs when handling hot containers.

Turn off burners that are not in use.

15

Precautions About Acids and Bases

When making dilute acids, slowly add acid to the water, not the other way

around.

Wear protective glasses or safety goggles to protect the eyes when handling

acids and bases.

When dilute acids or bases are spilled on the skin or in the eyes, immediately

wash the eyes or skin with plenty of water. Strong bases can cause burns. Weak

bases can cause burns when they are left in contact with the skin.

Fire Safety

Know where to locate water sources, gas outlets, and fire exits.

Know where to find the fire extinguishers, first aid kits, emergency showers, and

fire blankets in case of fire or injury.

If your clothes catch fire, do not run. Cover yourself with a wet blanket or roll on

the floor or use the shower.

If a person’s clothes have caught fire, lay the person down, roll the person over,

and smother the flames with a fire blanket.

Do not play with electrical sockets, gas fittings, or flammable chemicals in the

laboratory.

Completely extinguish matches after use an place them in a nonflammable

container. Do not throw matches into a waste basket.

Apparatus used in heating should be allowed to cool before storing them.

Hot objects should not be placed directly on the bench tops, paper, or other

flammable substances. A cool gauze mat should be used.

16

Disposal and Clean-Up

Note carefully the method of disposing chemicals in each activity.

Do not return excess chemicals back to their containers.

Clean up spills immediately, even if they are just water, to prevent accidents.

Before you leave the laboratory, do the following:

(1) Clean up the equipment you have used.

(2) Wipe your working table clean.

(3) Check that the water and gas outlets are closed.

(4) Place your stool under the table.

These safety rules should strictly be followed.

Better be safe than sorry . . .

17

FIRST AID

18

FIRST AID

Injury: Burns

What To Do: Immediately flush with cold water until

burning sensation is lessened.

Injury: Cuts, bruises

What To Do: Do not touch an open wound without

safety gloves. Pressing directly on minor

cuts will stop bleeding in a few minutes. Apply cold compress to

bruises to reduce swelling.

Injury: Fainting

What To Do: Provide fresh air and have the person recline

so that his head is lower than the rest of his

body.

19

First Aid

Injury: Poisoning

What To Do: Find out what substance was responsible for the

poisoning and alert the teacher immediately.

Injury: Spills on the skin

What To Do: Flush with large quantities of water. For acid spills, apply

baking soda solution. For base spills, apply vinegar or boric acid.

Injury: Electrical shock

What To Do: Shut off the current at the source. Remove wire with rubber

gloves. Alert the teacher immediately.

20

COMMON

LABORATORY

APPARATUS

21

COMMON LABORATORY APPARATUS

TEST TUBES as containers for holding chemicals

during heating or other reactions.

TEST TUBE RACKS used to support the test tubes.

TEST TUBE HOLDER used to hold the test tube

while heating

STIRRING ROD/ used for stirring or mixing chemicals

GLASS ROD

22

ERLENMEYER FLASKS / used as mixing vessels or

CONICAL FLASKS as containers for heating. They

give only approximate volumes.

VOLUMETRIC FLASKS used to measure one

specific volume of liquid.

GRADUATED CYLINDERS / used to measure volumes

MEASURING CYLINDERS of liquids in milliliters (ml)

BEAKERS used as containers for chemicals. They do not

give exact volumes of liquids.

23

PIPETTES measure and deliver exact volumes of liquid.

Graduated Pipette Volumetric Pipette

Pasteur’s Pipette (dropper)

PIPETTE AIDS / used with the pipette to take

PIPETTE FILLERS and deliver exact amount of liquid.

FUNNELS used to aid in the transfer of liquid from one

vessel to another

24

BUNSEN BURNER used for heating

DIGITAL BALANCE used to measure the mass of an

object in grams.

HOT PLATE STIRRER used as a heat source.

TRIPODS a three-legged stand used to

support the glass apparatus when heating

SPATULA used to spoon out or dispense solid

chemicals from their containers.

25

WIRE GAUZE used to protect glass apparatus

from direct application of heat

RINGSTAND/ IRON STAND used to support the burette,

and the burette clamp, and iron ring.

BURETTE CLAMP holds the burette

BURETTE used to dispense volumes of liquid in

titration.

BEAKER TONGS used to move beakers

containing hot liquids.

26

MEDICINE DROPPER used to transfer a small volume

of liquid. On top of each medicine

dropper is a rubber bulb.

WASH BOTTLES have spout that deliver wash

solution to a specific area.

Distilled water is the only liquid

that should be used in a wash

bottle.

REAGENT BOTTLES used to store small amount of chemicals

TEST TUBE BRUSH used to clean test tubes and

graduated cylinders.

EVAPORATING DISH are made from glazed porcelain and are used to hold samples under high heat conditions.

27

Student’S Activity MArkS

No. Experiment Title Mark

1 Solubility Test for Organic Compounds

2 Baeyer’s Test for Unsaturation

3 Bromine Test for Unsaturation

4 Physical Properties of Arenes (Benzene)

5 Lucas Test for 1o, 2o, and 3o Alcohols

6 Classifying Alcohols Using Acidified K2Cr2O7

7 Physical Properties of Aldehydes and Ketones

8 Tollen’s Test for Aldehydes

9 Fehling’s Test for Aldehydes

10 Iodoform Test for Methyl Ketones

11 Oxidation of Carbonyl Compounds by Acidified Potassium Dichromate

12 Oxidation of Carbonyl Compounds Using Fehling’s Solution

13 Fehling’s Test for Carbohydrates

Average

28

Experiment No. 1

SOLUBILITY TEST FOR ORGANIC COMPOUNDS

Experiment No. 1

SOLUBILITY TEST FOR ORGANIC COMPOUNDS

I. Introduction :

1. Hydrocarbons

Hydrocarbons are organic compounds that contain only carbon and hydrogen. Hydrocarbons can

either be aliphatic or aromatic. Aliphatic hydrocarbons contain either straight chains,

branched chains and/or certain cyclic arrangements of carbon atoms. Aromatic hydrocarbons

contain at least one aromatic ring, most commonly the benzene ring.

Alkanes are insoluble in polar solvents like water, but very soluble in non-polar solvents such as

other alkanes, diethylether, or carbon tetrachloride. Alkenes are insoluble in water but soluble in

organic solvents. The density of an alkene is less than that of water. Alkynes are colorless,

soluble in water and have a pleasant odor when pure.

2. Alcohol

The general formula of an alcohol is R-OH, where R is an organic group and –OH is the

hydroxyl group.

In general, alcohols with one –OH group and fewer than five carbon atoms are soluble in water,

but as the hydrocarbon chain gets longer, hydrogen bonding through the single –OH group is

not sufficient to keep the entire molecule in solution.

3. Aldehydes and ketones

Aldehydes and ketones are organic compounds which contain a carbonyl group (a

carbon-oxygen double bond).

In aldehydes, the carbonyl group has a hydrogen atom attached to it together with either:

a second hydrogen atom

a hydrocarbon group which might be an alkyl group or one containing a benzene ring.

Batterjee Medical College for Science and Technology Department of Chemistry – Chemistry Practical

Name : _____________________________________

Class : ________________ ID No. _____________

29

In ketones, the carbonyl group has two hydrocarbon groups attached. Ketones never have a

hydrogen atom attached to the carbonyl group.

In general, aldehydes and ketones with fewer than five carbon atoms will be completely soluble

in water, but as the number of carbon atoms increases, the solubility decreases.

4. Carboxylic Acid

Carboxylic acids are Bronsted-Lowry acids because they are proton (H+) donors.

Smaller carboxylic acids (1 to 5 carbons) are soluble in water, whereas higher carboxylic acids

are less soluble due to the increasing hydrophobic nature of the alkyl chain. These longer chain

acids tend to be rather soluble in less-polar solvents such as ethers and alcohols.

Carboxylic Acid Ester

5. Esters

The small esters are fairly soluble in water but solubility falls with chain length.

The reason for the solubility is that although esters can't hydrogen bond with themselves, they

can hydrogen bond with water molecules.

One of the slightly positive hydrogen atoms in a water molecule can be sufficiently attracted to

one of the lone pairs on one of the oxygen atoms in an ester for a hydrogen bond to be formed.

30

II. Objective:

Describe the solubility of organic compounds in polar and non-polar solvents.

III. Materials :

Test tubes (12) test tube rack acetaldehyde

Pasteur’s pipette water oxalic acid

Hexane methanol acetone

Sodium benzoate diethylether

IV. Procedure :

1. Put 1 ml of hexane in the first tube, and 1 ml in the second tube. Add 1 ml of water in

the first tube. Add 1 ml of diethylether in the second tube.

2. Note the observation. Record in the report sheet below.

3. Do the step one for the rest of the compounds listed in the report sheet. Record your

observations below.

Report Sheet:

Organic Compound Water Diethyl Ether

Hexane

Methanol

Acetaldehyde

Acetone

Oxalic acid

Sodium benzoate

Note :

miscible - clear solution with no layering

immiscible - cloudy mixture or two separate layers

31

Experiment No. 2

BAEYER’S TEST FOR UNSATURATION

I. Introduction :

Alkenes and alkynes are both unsaturated hydrocarbons. Baeyer’s permanganate test

is a test used to distinguish whether the hydrocarbon is saturated or not. In this test, the

hydrocarbon is made to react with dilute potassium permanganate, KMnO4. As the reaction

proceeds, the characteristic color of the permanganate ion is destroyed and replaced by a brown

to black suspension of finely divided manganese (IV) oxide, MnO2. The color change of the

solution from purple to brown (or black) indicates the presence of an alkene or an alkyne.

H H

C = C + KMnO4 C - C + MnO2(s)_

H H OH OH

potassium manganese

alkene permanganate a diol (IV) dioxide

(colorless) (purple) (colorless)


Name : _____________________________________

Class : _________________ ID No. ______________

32

II. Objective:

Distinguish saturated from unsaturated hydrocarbon using Baeyer’s permanganate test

III. Materials :

saturated hydrocarbon 2 test tubes

unsaturated hydrocarbon test tube rack (small)

0.5% KMnO4 solution plastic droppers

IV. Procedure :

1. Put 3 ml of compound A and 3 ml of compound B in two separate test tubes.

2. Add 2 – 3 drops of 0.5% KMnO4 solution into each of the two labeled test tubes.

3. Shake the mixture for about 1 minute. The color change of the solution from purple to brown

(or black) indicates the presence of an unsaturated hydrocarbon.

V. Report Sheet :

Compound Tested

Observations

Saturated or Unsaturated

Hydrocarbon

A

B

33

Experiment No. 3

BROMINE TEST FOR UNSATURATION

I. Introduction :

Alkanes are saturated hydrocarbons because of the presence of carbon to carbon single

bond. Alkenes are unsaturated hydrocarbons which contain double carbon – carbon covalent

bonds.

Bromine test is a test used to determine whether the hydrocarbon is saturated or not.

The decolorization of bromine is a test to distinguish between saturated and unsaturated

hydrocarbons. Only unsaturated ones will decolourise bromine water easily.

II. Objective :

Distinguish saturated from unsaturated hydrocarbon using bromine test.

III. Materials :

saturated hydrocarbon test tube rack

unsaturated hydrocarbon 2 test tubes

bromine solution plastic dropper


Name : ____________________________________

Class : _______________ ID No. _______________

34

IV. Procedure :

1. Put 3 ml of compound A and 3 ml of compound B in two separate test tubes.

2. Add 5 drops of bromine solution into each of the two test tubes.

3. Shake both solutions thoroughly. Decolorization of bromine is a positive test for the presence

of double bond or triple bond.

V. Report Sheet :

Compound Tested

Observations

Saturated or Unsaturated

Hydrocarbon

A

B

35

Experiment No. 4

PROPERTIES OF ARENES or AROMATIC COMPOUNDS (BENZENE)

I. Introduction:

Benzene is the first and principal member of the series of aromatic hydrocarbons. It

has a pleasant odor and colorless at room temperature. It is insoluble in water but soluble in

most non-polar inorganic solvents.

Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a

ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula of C6H6.

It is an aromatic hydrocarbon, a cyclic hydrocarbon with a continuous pi-bond. It is

colorless and highly flammable liquid with a sweet smell. To test one of its chemical properties

is by burning. When burned, it produces a yellow flame with black smoke and black soot.

II. Objective:

Test the solubility of benzene in different solvents.

III. Materials :

Benzene propanone (acetone) methanol

Water 3 test tubes test tube rack (small)


Name : _____________________________________

Class : _________________ ID No. ______________

36

IV. Procedure :

1. Place 1 ml of benzene into each of the three test tubes.

2. Add 1 ml of water in the first test tube.

3. Shake the mixture thoroughly and set it aside in a test tube rack.

4. Do the same to the rest of the compounds (acetone and methanol) to the 2nd and 3rd test

tubes respectively.

5. After 5 minutes, observe each mixture. If the substance is insoluble, a cloudy mixture or two

separate layers are formed. If it is soluble, a clear (transparent) solution with no layering is

observed.

V. Report Sheet:

Compound Tested

Miscible or Immiscible

Water + benzene

Acetone + benzene

Methanol + benzene

37

Experiment No. 5

CLASSIFYING ALCOHOLS AS 1o, 2o, OR 3o BY LUCAS TEST

I. Introduction :

The Lucas reagent is a mixture of ZnCl2 in concentrated hydrochloric acid, HCl. It is used

to determine whether an alcohol is primary (1o), secondary (2o), or tertiary (3o).

The Lucas reagent will convert a soluble alcohol to an insoluble alkyl chloride according to

the reaction:

ZnCl2

R – OH + H – Cl R – Cl + H2O

The appearance of a milky suspension in the reaction mixture indicates the reaction has taken

place. Tertiary alcohols react immediately. Secondary alcohols take time to react. Primary

alcohols will show no reactivity with Lucas reagent.

II. Objective:

Classify alcohol as to primary or tertiary based on the reaction with Lucas reagent.

III. Materials :

ethanol 2 test tubes

tert. butanol plastic dropper

Lucas reagent

Batterjee Medical College for Science and Technology

Department of Chemistry – Chemistry Practical

Name : _____________________________________

Class : ________________ ID No. _______________


Name : _____________________________________

Class : _________________ ID No. _____________

38

IV. Procedure :

Caution ! Lucas reagent contains concentrated

hydrochloric acid (HCl). It is toxic and

corrosive. Handle it with care.

1. Put 1 ml of alcohol into each of the two test tubes. Using a dropper, add about 1 ml of Lucas

reagent drop wise/ slowly.

2. Record your observations for each alcohol in the Report Sheet. Then classify the alcohol as to

primary or tertiary alcohol.

V. Report Sheet :

Alcohol

Observations

Primary or Tertiary Alcohol

Alcohol No. 1

Alcohol No. 2

39

Experiment No. 6

CLASSIFYING ALCOHOLS BY USING ACIDIFIED POTASSIUM DICHROMATE

I. Introduction :

Alcohols can be oxidized by strong oxidants, such as K2Cr2O7 in H2SO4, but differs

depending on the degree of alcohol

O

ll

RCH2OH + K2Cr2O7 C + Cr+3

R H

a primary alcohol orange aldehyde green/blue

O

ll

CH3CH2OH + Cr+6 Cr+3 + C

CH3 H

a primary alcohol orange green/blue an aldehyde

further oxidation

O

ll

C

CH3 OH

carboxylic acid


Name : _____________________________________

Class : _________________ ID No. _____________

40

As the alcohol is oxidized, the Cr+6 is reduced to Cr+3, which turns the orange color of the

solution to blue-to-green color. The appearance of the blue-to-green color within one minute is

considered a positive test for a primary or a secondary alcohol.

OH O

l ll

CH3 - C – CH3 + Cr+6 Cr+3 + CH3 – C – CH3

l

H

a secondary alcohol orange green/blue a ketone

no further oxidation

OH

l

CH3 - C – CH3 + Cr+6 no reaction (still orange)

l

CH3

a tertiary alcohol orange

II. Objective:

Classify alcohol as to primary or tertiary using acidified dichromate (VI) solution.

41

III. Materials :

ethanol 2 test tubes

tert. butanol plastic dropper

acidified K2Cr2O7

IV. Procedures :

1. Put 1 ml of alcohol A into test tube A, and 1 ml of alcohol B into test tube B.

2. Add 2 ml of acidified K2Cr2O7 solution into each of the previously labeled test tubes.

3. Place the two test tubes in a warm water bath.

4. After 5 minutes, note any color change and record your observations on the report sheet.

V. Report Sheet :

Alcohol Observations Alcohol Classification

(1oor 3o)

A

B

42

Experiment No. 7

PHYSICAL PROPERTIES OF ALDEHYDES AND KETONES

I. Introduction :

In general, aldehydes and ketones with fewer than five carbon atoms will be completely

soluble in water, but as the number of carbon atoms increases, the solubility decreases. The

reason for this lies in the fact that only the carbonyl group can be accommodated by water

through hydrogen bonding and dipole-dipole interactions. If the carbon chains are not large, the

interaction of the carbonyl group with water is sufficient to keep the entire molecule in solution.

But as the number of carbon atoms increases, the water-repelling character of the carbon chain

overwhelms the water-loving nature of the carbonyl group and it is difficult for the organic

molecule to stay in the solution.

II. Objective:

Test the solubility of aldehydes and ketones in water.

III. Materials :

formaldehyde 3 test tubes

propanone (acetone) test tube rack (small)

pentanone


Name : _____________________________________

Class : _________________ ID No. ______________

43

IV. Procedure :

1. Label the three test tubes as A, B and C

2. Place 2 ml of distilled water into each of the three previously labeled test tubes.

3. Add 2 ml of each compound to be tested into the appropriate test tube.

4. Shake each mixture thoroughly and set it aside in a test tube rack.

5. After 5 minutes, observe each mixture. If the substance is insoluble in water, a cloudy

mixture or two separate layers are formed. If it is soluble, a clear (transparent) solution with no

layering is observed.

V. Report Sheet :

Compound Tested

Miscible or Immiscible

A

B

C

Note :

miscible - clear solution with no layering

immiscible - cloudy mixture or two separate layers

44

Experiment No. 8

TOLLENS’ TEST FOR ALDEHYDES

I. Introduction :

Aldehydes can be distinguished from ketones by the Tollens’ test, because aldehydes are

easily oxidized to carboxylic acids, while ketones are not. Tollens reagent is a solution of silver

nitrate in aqueous ammonia. Silver ion is the oxidizing agent and is reduced to silver metal as

the aldehyde is oxidized to carboxylic acid. The positive Tollens’ test is the appearance of a

mirror of silver metal on the wall of the test tube, or a dark gray to black precipitate of silver

metal.

RCHO + 2 [Ag(NH3)2] + 2OH- -- RCOO -, NH4+ + 2 Ag + H2O + 3NH3

Aldehyde Tollens’ reagent soluble salt silver

of the acid mirror

II. Objective:

Distinguish aldehydes from ketones using the Tollens’ silver mirror test.

III. Materials :

test tubes Tollens’ reagent

test tube rack acetaldehyde

medicine dropper acetone


Name : _____________________________________

Class : _______________ ID No. _______________

45

IV. Procedure :

1. Put 2ml of 5% AgNO3 solution in each test tube. Then add 2 drops of 5% NaOH.

2. Add 1ml of 1M NH4OH solution (aqueous ammonia) until the initial precipitate just dissolves.

3. Add 4 drops of compound A into the first test tube and 4 drops of compound B into the

second test tube

4. Mix each well and warm the test tubes in a water bath for 3 up to 5 minutes. If the test tube

is clean, a silver mirror on the glass surface constitutes a positive test; otherwise, a gray or

gray-black precipitate of silver metal is the positive test.

V. Report Sheet :

Indicate whether you observed a positive reaction (+) or negative reaction (-) in each of the

following compounds using the Tollens’ test. Write down your observations. Then classify the

compound as to aldehyde or ketone.

Compound

Tested

Positive or Negative

Reaction with

Tollen’s Test

Observations

Aldehyde

or

Ketone

Compound A

Compound B

46

Experiment No. 9

FEHLING’S TEST FOR ALDEHYDES

I. Introduction :

Aldehydes can be distinguished from ketones by the Fehling’s test. Aldehydes are easily

oxidized to carboxylic acids because a hydrogen atom is attached to the carbonyl, while ketones

are not.

acetaldehyde (an aldehyde) acetone (a ketone)

Aldehydes can be oxidized by a mild oxidizing agent like Cu+2 in alkaline solution used in

Fehling’s test. Fehling’s reagent is a deep blue Cu+2 solution that forms a brick –red precipitate

of Cu2O in the presence of aldehydes.

II. Objective:

Distinguish aldehydes from ketones using Fehling’s test.

III. Materials :

Fehling’s solution (A and B) 2 test tubes

acetaldehyde test tube rack (small)

acetone medicine dropper

100-ml beaker (1) hot plate


Name : _____________________________________

Class : _______________ ID No. _______________

47

IV. Procedure :

1. Mix 1 ml of Fehling’s solution A with 1 ml of Fehling’s solution B in each of the two test

tubes.

2. Then add 1 ml of compound A into the first tube and 1 ml of compound B into the second

tube.

3. Make sure of the tubes with compound A and compound B, before placing them in the water

bath.

4. Heat the mixture for 3 – 5 minutes in a water bath and take note of any changes in color or

formation of precipitate.

V. Report Sheet :

Compound Tested

Positive Reaction or

Negative Reaction with

Fehling’s Test

Observations

Aldehyde

or

Ketone

Compound A

Compound B

48

Experiment No. 7

IODOFORM TEST FOR METHYL KETONES

Experiment No. 10

IODOFORM TEST FOR METHYL KETONES

I. Introduction :

The iodoform test or reaction is a reaction where iodoform (CHI3) is produced by the

multiple halogenation of a methyl ketone ( a molecule containing the R- CO – CH3 group ) in

the presence of a base. It is a chemical test used for the detection of ketones and aldehydes

carrying a methyl group. The reagents are iodine and sodium hydroxide.

Iodine solution is added to a small amount of aldehyde or ketone, followed by just

enough sodium hydroxide solution to remove the color of the iodine.

A positive result is the appearance of a very pale yellow precipitate of triiodomethane

(previously known as iodoform) – CHI3. It is given by an aldehyde or ketone containing the

grouping:

O

CH3 – C

R

“R” can be a hydrogen or a hydrocarbon group (for example, an alkyl group).

If “R” is a hydrogen, then you have an aldehyde ethanal, CH3CHO.

Ethanal is the only aldehyde to give the triiodomethane (iodoform ) reaction.

If “R” is a hydrocarbon group, then you have a ketone. Those ketones that do have a

methyl group on one side of the carbon-oxygen double bond will give this reaction.


Name : _____________________________________

Class : _______________ ID No. ________________

49

II. Objective:

Identify the presence of a CH3CO group in aldehydes and ketones using the iodoform

reaction.

III. Materials :

acetaldehyde acetic acid iodine solution

benzaldehyde butanone 5 test tubes

acetone 0.1N NaOH solution droppers

IV. Procedure :

1. Put 1 ml of acetaldehyde into the first test tube, 1 ml of benzaldehyde into the second

test tube, 1 ml of acetone into the third, 1 ml of butanone into the fourth and 1 ml of acetic

acid into the fifth.

2. Add 3 – 4 drops of iodine solution into each of the test tubes.

3. Add 0.1N NaOH solution drop wise into each of the test tubes until the light yellow

precipitate appears.

4. Record your observations on the report sheet.

50

V. Report Sheet :

Compound

Observations

acetaldehyde

benzaldehyde

acetone

butanone

acetic acid

Question:

Which of the following compounds give positive result and why?

____________________________________________________________________________

____________________________________________________________________________

51

Experiment No. 5

Experiment No. 11

OXIDATION OF CARBONYL COMPOUNDS USING ACIDIFIED POTASSIUM (VI)

DICHROMATE

I. Introduction :

The carbonyl group is common to both aldehydes and ketones. In aldehydes, the

carbonyl group always has a hydrogen bonded to it. Because the aldehyde group must include

at least one hydrogen atom with the carbonyl, the aldehyde function will always appear at the

end of a carbon chain.

(the aldehyde functional group)

The aldehyde functional group can be condensed to –CHO, and the general formula for an

aldehyde can be written as R-CHO. Note that the H comes before the O in the aldehyde

formula , but after the O in alcohols.

In ketones, the carbonyl group is always bonded to two other carbon atoms, never directly to a

hydrogen atom.

(the ketone functional group)

The ketone functional group can be condensed to RCOR, in which R is either an alkyl or aryl

(aromatic) group.


Name : _____________________________________

Class : _________________ ID No. ______________

52

II. Objective :

Compare the oxidation of aldehyde and ketone using acidified potassium dichromate

(VI).

III. Materials :

ethanal (acetaldehyde) 2 test tubes

propanone (acetone) test tube rack (small)

acidified potassium dichromate (VI) solution plastic droppers

IV. Procedure :

1. Put 1 ml of acidified potassium dichromate (VI) solution into each of the two test tubes.

2. Then add 5 drops of acetaldehyde into the first tube and 5 drops of acetone into the second

tube.

3. Observe which of the two compounds will react with acidified K2Cr2O7.Then write down your

observations on the report sheet.

V. Report Sheet :

Compound Tested

Positive Reaction or

Negative Reaction with

Acidified Potassium

Dichromate (VI)

Observations

Acetaldehyde

Acetone

53

Experiment No. 12

OXIDATION OF CARBONYL COMPOUNDS BY FEHLING’S SOLUTION

I. Introduction :

Sugar is a sweet-tasting soluble naturally occurring carbonyl compound. Sugars such as

glucose show many properties that are typical of carbonyl compounds.

Fehling’s test has been used to detect sugar in the urine of people suffering from

diabetes. The pancreas of these patients produces insufficient insulin to cope with the sugar in

their diet. This means that the sugar accumulates in the blood and, when it reaches a certain

concentration, it is excreted by the kidney, and appears in the urine. Depending on the

concentration of glucose, the solution may simply turn green, produce a fine yellow precipitate

or give a dark red precipitate.

II. Objective :

Show the oxidation of a carbonyl compound using Fehling’s solution.

III. Materials :

Fehling’s solution 2 test tubes

glucose test tube rack (small)

spatula hot plate

water beaker, 250 ml


Name : _____________________________________

Class : _________________ ID No. ______________

54

IV. Procedure :

1. Put 2 ml of distilled water in one of the test tubes. Then dissolve one spatula of

glucose. Keep it aside in the test tube rack.

2. In another tube, prepare Fehling’s solution by mixing together 3 ml of Fehling A with 3

ml of Fehling B.

3. Then add the Fehling’s solution into the glucose-water mixture.

5. Boil the mixture gently. Write down your observation in the Report Sheet.

V. Report Sheet :

Describe and explain what happens when Fehling’s solution is added to glucose-water mixture.

__________________________________________________________________________

__________________________________________________________________________

55

\

Experiment No.13

FEHLING’S TEST FOR CARBOHYDRATES

I. Introduction :

A carbohydrate is an organic compound that consists only of carbon, hydrogen, and

oxygen.

The term is most common in Biochemistry, where it is a synonym of saccharide. The

carbohydrates (saccharides) are divided into three chemical groupings.

1. Monosaccharide

2. Disaccharide

3. Polysaccharide

Monosaccharide - general formula (CH2O)n

If the carbonyl group is an aldehyde, the monosaccharide is an aldose; if the carbonyl

group is a ketone, the monosaccharide is a ketose.

Examples : glucose, fructose and glyceraldehydes

Disaccharide - two joined monosaccharide and these are the simplest polysaccharides

Disaccharides can be classified into two types.

1) reducing disaccharides or biose - if the functional group is present in bonding with

another sugar unit (open-structure)

2) Non-reducing disaccharides - if the functional group is cannot bond with another sugar

unit (closed-structure)

Examples include sucrose and lactose.


Name : _____________________________________

Class : _______________ ID No. ________________

56

Polysaccharides are long carbohydrate molecules of repeated monomer units. General

formula of Cx(H2O)y

Types of Polysaccharide:

1. homopolysaccharide or homoglycan - when all the monosaccharides in a polysaccharide

are the same type

2. heteropolysaccharides or heteroglycans - when more than one type of monosaccharide

Examples : starch and glycogen

II. Objective :

Determine the carbohydrate by using Fehling’s Test.

III. Materials:

Fehling A solution Fehling B solution

Sucrose test tubes (3)

Fructose test tube rack

Glucose Pasteur’s pipette

Hot plate beaker

IV. Procedure :

1. Mix 1 ml of Fehling’s solution A with 1 ml of Fehling’s solution B in each of the three test

tubes.

2. Then add 1 ml of compound A into the first tube, and 1 ml of compound B into the

second tube, and 1 ml of compound C into the third tube.

3. Make sure of the tubes with compounds A, B and C, before placing them in the water

bath.

4. Heat the mixture for 3 – 5 minutes in a water bath and take note of any changes in

color or formation of precipitate.

57

V. Report Sheet :

Fehling’s Test used to determine the carbohydrate. A positive result will show a

brick-red precipitate.

Carbohydrate Positive / Negative

Glucose

Sucrose

Fructose

Question:

What sugar/s gave a positive result with Fehling’s Test ? Why?

_____________________________________________________________

_______________________________________________________________________

Chemistry Lab Manual_2nd Sem 2012-2013.pdf

Documents

Transcript of Chemistry Lab Manual_2nd Sem 2012-2013.pdf