ComprehensiveCHEMISTRY ACTIVITIES

Volume I

FOR CLASS XI

Strictly according to the latest curriculum prescribed by

Central Board of Secondary Education (CBSE)and

State Boards of Chhattisgarh, Haryana, Bihar, Jharkhand, Kerala, Mizoram,Meghalaya, Uttarakhand and other States following NCERT Curriculum

By

Dr. N.K. VERMAAssociate Professor

Chemistry DepartmentD.A.V. College

Chandigarh

Name ...........................................................................................

School ..........................................................................................

Class ..................................... Section ........................................

School Roll No. ....................... Examination Roll No. ......................

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Chapters Pages

Syllabus (vii)—(viii)

1. Basic Laboratory Techniques 1–3

2. Determination of Melting Point and Boiling Point 4–6Exp-2.1 : To determine the melting point of the given organic compound. ... 4Exp-2.2 : To determine the boiling point of liquid organic compound. ... 5

3. Purification of Chemical Substances by Crystallization 7–11Exp-3.1 : To prepare crystals of pure copper sulphate (CuSO4.5H2O) from a given impure

sample of the blue vitriol. ... 9Exp-3.2 : To prepare the crystals of potash alum, K2SO4.Al2(SO4)3.24H2O from the crude

sample. ... 10Exp-3.3 : To purify impure sample of benzoic acid by the process of crystallization. ... 11

4. Experiments Based on pH Change 12–18Exp-4.1 : Determine the pH of vegetable and fruit juices using pH paper and universal

indicator. ... 12Exp-4.2 : Determine the pH values of hydrochloric acid at different strengths using: (i) pH

papers and (ii) universal indicator solution. ... 13Exp-4.3 : To determine the pH of various samples of NaOH solution using : (i) pH paper

and (ii) universal indicator solution. ... 14Exp-4.4 : Determine the pH of solutions of some salts using pH paper or universal indicator. ... 15Exp-4.5 : Compare the pH of solutions of hydrochloric acid and acetic acid having same

concentration. ... 16

Exp-4.6 : Study the pH change in the titration of M10

HCl with M10

NaOH usinguniversal indicator. ... 16

Exp-4.7 : To study the change in pH of acetic acid solution on addition of sodium acetate. ... 17Exp-4.8 : To study the change in pH of ammonium hydroxide solution on addition of

ammonium chloride. ... 18

5. Effect of Change of Concentration on Chemical Equilibrium 19–20Exp-5.1 : To study the shift of equilibrium between ferric ions and thiocyanate ions by

increasing the concentrations of either of them. ... 19

6. Quantitative Estimation (Volumetric Analysis) 21–31

Exp-6.1 : Prepare M10

sodium carbonate solution. ... 23

Exp-6.2 : Prepare M10

oxalic acid solution. ... 24

Exp-6.3 : To determine the molarity and the strength of the given sodium hydroxide

solution. You are provided with M10

oxalic acid solution. ... 27

( v )

Contents

Exp-6.4 : Standardise the given solution of hydrochloric acid which is approximately 0.1 M.You are provided with 0.05 M Na2CO3 solution. ... 28

Exp-6.5 : Determine the percentage purity of the given sample of caustic soda, 5.0 g ofwhich are dissolved per litre. Ask for your requirement. ... 29

Exp-6.6 : The given solution contains 6.3 g of hydrated oxalic acid, COOH

COOH⏐ . nH2O, crystals

per litre. Determine the value of n (no. of molecules of water of crystallization).Provided 0.1 M NaOH. ... 30

7. Qualitative Analysis 32–47Exp-7.1 : To analyse the given salt for acidic and basic radicals. ... 45

8. Detection of Nitrogen, Sulphur, Chlorine, Bromine and Iodinein an Organic Compound 48–50Exp-8.1 : Detection of N, S, Cl, Br and I in an organic compound. ... 50

INVESTIGATORY PROJECTS

1. Study of Methods of Purification of Water 51

2. Analysis of Hard Water 53Exp-1 : To determine the hardness of a water sample. ... 54

3. To Study the Foaming Capacity of Soaps 56Exp-1 : Compare the foaming capacities of different samples of soaps. ... 56Exp-2 : Study the effect of addition of sodium carbonate (washing soda) on the foaming

capacity of a soap. ... 57

4. To Study the Rate of Evaporation of Different Liquids 58Exp-1 : To compare the rates of evaporation of water, acetone and diethyl ether. ... 59Exp-2 : To study the effect of surface area on the rate of evaporation of diethyl ether. ... 60Exp-3 : To study the effect of temperature on rate of evaporation of acetone. ... 60Exp-4 : To study the effect of air current on the rate of evaporation. ... 61

5. Study of the Effect of Acids and Bases on the Tensile Strength of Fibres 61Exp-1 : To compare tensile strength of cotton, silk and nylon fibres. ... 62Exp-2 : To find the effect of acids and alkalies on tensile strength of cotton,

wool and silk fibres. ... 63

6. Preparation of an Alum from Scrap Aluminium 63Exp-1 : To prepare potash alum from scrap aluminium. ... 64

Chapters Pages

( vi )

( vii )

CHEMISTRYCLASS XI (PRACTICALS)

Evaluation Scheme for Examination Marks

Volumetric Analysis 10Salt Analysis 8Content Based Experiment 6Class Record, Project and Viva 6

Total 30

Practicals SyllabusMicro-chemical methods are available for several of the practical experiments. Wherever possible suchtechniques should be used:

A. Basic Laboratory Techniques (Periods 2)1. Cutting glass tube and glass rod2. Bending a glass tube3. Drawing out a glass jet4. Boring a cork

B. Characterization and Purification of Chemical Substances (Periods 6)

1. Determination of melting point of an organic compound.2. Determination of boiling point of an organic compound.3. Crystallization of an impure sample of anyone of the following: Alum, Copper sulphate, Benzoic acid.

C. Experiments Based on pH (Periods 6)(a) Anyone of the following experiments:

• Determination of pH of some solutions obtained from fruit juices, solution of known and varied concentra-tions of acids, bases and salts using pH paper or universal indicator.

• Comparing the pH of solutions of strong and weak acids of same concentration.• Study the pH change in the titration of a strong base using universal indicator.

(b) Study the pH change by common-ion in case of weak acids and weak bases.

D. Chemical Equilibrium (Periods 4)One of the following experiments:(a) Study the shift in equilibrium between ferric ions and thiocyanate ions by increasing/decreasing the concen-

tration of either ions.(b) Study the shift in equilibrium between [Co(H2O)6]

2+ and chloride ions by changing the concentration ofeither of the ions.

E. Quantitative Estimation (Periods 12)(i) Using a chemical balance.

(ii) Preparation of standard solution of oxalic acid.

Syllabus

(iii) Determination of strength of a given solution of sodium hydroxide by titrating it against standard solution ofoxalic acid.

(iv) Preparation of standard solution of sodium carbonate.(v) Determination of strength of a given solution of hydrochloric acid by titrating it against standard sodium

carbonate solution.

F. Qualitative Analysis (Periods 16)(a) Determination of one anion and one cation in a given salt

Cations: Pb2+, Cu2+, As3+, Al3+, Fe3+, Mn2+, Ni2+, Zn2+, Co2+, Ca2+, Sr2+, Ba2+, Mg2+, NH4+.

Anions: CO32–, S2–, SO3

2–, SO42–, NO2

–, NO3–, Cl–, Br–, I–, PO4

3–, C2O42–, CH3COO–.

(Note: Insoluble salts excluded).(b) Detection of nitrogen, sulphur, chlorine in organic compounds.

PROJECTS(Periods 10)

Scientific investigations involving laboratory testing and collecting information from other sources.A Few Suggested Projects

• Checking the bacterial contamination in drinking water by testing sulphide ion.• Study of the methods of purification of water.• Testing the hardness, presence of iron, fluoride, chloride, etc., depending upon the regional variation in

drinking water and study of causes of presence of these ions above permissible limit (if any).• Investigation of the foaming capacity of different washing soaps and the effect of addition of sodium carbon-

ate on them.• Study of the acidity of different samples of tea leaves.• Determination of the rate of evaporation of different liquids.• Study of the effect of acids and bases on the tensile strength of fibers.• Study of activity of fruit and vegetable juices.

Note: Any other investigatory project, which involves about 10 periods of work, can be chosen with the approval ofthe teacher.

( viii )

INDEX

S. No. EXPERIMENT DATE OF SIGN.WORK

INDEX

S. No. EXPERIMENT DATE OF SIGN.WORK

INDEX

S. No. EXPERIMENT DATE OF SIGN.WORK

INDEX

S. No. EXPERIMENT DATE OF SIGN.WORK

1.1. CUTTING A GLASS TUBE

Cutting a glass tube is primarily required for making U-shaped tubes, delivery tubes and other purposes.Hence, a student must know how to cut glass tube of required length for specified purpose without injuring hands.For cutting a glass tubing proceed in the following manner:

1. Select a glass tubing free of cracks.2. Place it on the bench, hold it firmly and make a single deep scratch with triangular file. Do not apply too

much pressure.3. Place the thumbs on each side of the scratch at equal distances from it. Apply gentle pressure and give a

quick bending motion towards you until it breaks smoothly.4. Sometimes, the ends of the tube are not smooth and might bruise your fingers. These can be smoothened

by rotating the ends in a flame for 2–3 minutes. The edges will be smoothened. This is called fire polishing.Allow it to cool while holding in your hand.

Pull Triangular fileScratch

Fig. 1.1. Making a groove. Fig. 1.2. Breaking the glass tube at the scratch.

PRECAUTIONS

1. Make a single deep scratch at the desired length with one stroke of the file.2. To avoid injury hold the glass tube with the help of a thick piece of cloth.

1.2. BENDING A GLASS TUBE

For bending a glass tube proceed as follows:1. Hold the glass tube between the thumb and fingers, introduce it lengthwise in the luminous flame of

burner. Keep the tube rotating till it softens.2. Now apply gentle pressure so that it bends by itself. When the desired angle is formed, remove the tube

from the flame.3. Place the bent limb on the asbestos sheet. Press it gently so as to make it coplanar. Allow the tube to cool.

1

CHAPTER 1Basic Laboratory Techniques

2 COMPREHENSIVE CHEMISTRY ACTIVITIES VOL. I—XI

Hot end

Asbestossheet

(a) (b) (c)

Fig. 1.3. (a) Heating the tube, (b) The tube softens and starts bending under its own weight, (c) Making the bend coplanar.

PRECAUTIONS

1. Select a glass tube of sufficient length to keep your hands safe from heat. Do not try to bend very smallglass tubes of the lengths less than 20 cms.

2. While heating, the glass tube should be rotated in order to ensure uniform heating.

1.3. DRAWING A GLASS JET

1. Take a glass tube of required length and diameter. Hold it with both hands and place it lengthwise inflame (Fig. 1.4).

1. Heat the tubing in the bunsen flamewhile rotating between fingers.

2. Continue heating and rotating with inwardpressure till the tube in the centre becomes

very soft.

3. Remove the tubing from the flame and after amoment pull the ends apart to get the

narrow capillary in the middle.

4. Cut to length and fire-polish thetwo ends of droppers.

Before cutting

Jet

Fig. 1.4. Drawing a jet.

BASIC LABORATORY TECHNIQUES 3

2. Keep rotating the tube so as to ensure uniform heating, continue heating till it softens.3. Take the tubing out of the flame and gently pull the two ends apart. The middle portion is drawn out to a

thickness of about 2 mm.4. Cool and cut the narrow portion with a triangular file and two jets will be obtained. Finally round the

ends of the jets by heating in a flame for a short while.

PRECAUTION

1. While drawing a jet, pull apart the two ends of the red-hot tube slowly, so that it becomes thin uniformly.

1.4. BORING A CORK

Boring a cork is required for setting up an apparatus for the preparation of gas and for carrying out distilla-tion etc. Above all, it is required for fitting up a wash bottle. For perfect boring of the cork, the following steps areinvolved:

1. Softening of the Cork. It is essential as a cork gets hard on keeping. In order to soften a cork, wet it withwater. When it becomes flexible and does not crack readily, then press it in a cork-presser which is a mechanical deviceand if it is not available, simply press the wetted cork under your shoes after wrapping the cork in a piece of paper.

2. Selection of the Borer. Choose a borer slightly smaller in diameter than that of the tube to be fitted inthe cork. This will ensure tight fitting of the tube.

3. Boring of the Cork. Place the cork on the table with its narrow end upward. Mark the position of theborer on both the sides of the cork to ensure straight hole. Holding the cork tightly with left hand, apply force on theborer with a twisting motion. Apply some glycerine to the borer if it is a rubber cork. Glycerine acts as lubricant forthe hard rubber cork. When half of the cork has been bored, take the borer out and reverse the cork. Start theprocess of boring taking care that the borer remains vertical throughout. Remove the borer after the cork has beenbored from one face to the other. Remove the pieces of the cork inside by inserting the needle.

Fitting the Glass Tube in the Bore. Wet the cork with water or glycerine. Wet the end of the tube also withwater or glycerine. Hold the cork in one hand say left hand and tube in the right hand. It should be noted that thetube should be held closely from the wetted end. Insert the tube into the bore giving a rotatory motion.

Place marked for boring

Glass tube Borer

(a) (b) (c)

Fig. 1.5. (a) Marked cork (b) Choosing the borer (c) Boring process.

Note. Since the rubber is hard, the end of the tube to be inserted is usually dipped in caustic soda solution or glycerinebefore fitting in the hole.

PRECAUTIONS

1. Select borer of diameter slightly smaller in size than that of the tube to be inserted in the hole.2. Make a mark on both sides of the cork.3. To obtain a smooth hole, drill half the hole from one side and another half from the other side of the cork.

The melting point of a substance may be defined as the temperature at which the substance changes from thesolid state to the liquid state. It is a very useful physical constant because a pure substance melts at a definitetemperature and has a sharp melting point while an impure substance has a lower melting point and melts overa wide range. Therefore, determination of melting point is a very convenient method to check the purity of a solidsubstance. Moreover, melting point determination can be used to identify a substance by comparing its meltingpoint with the melting points of known substances.

The boiling point of a liquid may be defined as the temperature at which the vapour pressure of the liquid isequal to the atmospheric pressure exerted upon the liquid surface.

The normal boiling point of a liquid may be defined as the temperature at which vapour pressure of theliquid is equal to one standard atmospheric pressure.

The boiling point of a liquid increases if non-volatile impurities are present in it.

EXPERIMENT 2.1 To determine the melting point of the given organic compound.

REQUIREMENTS

100 ml beaker, thermometer, iron stand, clamp, tripod stand, stirrer, thin-walled capillary tube 8 to 10 cmlong and 1 to 2 mm diameter, spatula.

Liquid paraffin or concentrated sulphuric acid.

PROCEDURE

1. Powder the crystalline compound. Take a capillary tube and sealits one end by heating (Fig. 2.1). Fill small amount of thecompound into it. For filling the compound make a heap of thepowdered compound on the porous plate. Push the open end ofthe capillary tube into the heap. Some compound will enter intoit. Now tap the sealed end of the capillary tube on the porousplate gently. Fill the capillary tube up to 2–3 mm.

2. Attach the capillary tube to a thermometer which is immersedin a bath of suitable liquid. The surface tension of the bath liquidis sufficient to hold the capillary tube in position.

3. Heat the beaker slowly and go on stirring the liquid in the beakerso that the temperature remains uniform throughout. For this,a glass loop stirrer is moved up and down. When the temperatureis within 15° of the melting point of the pure compound, theflame is lowered. Now, the temperature is allowed to rise slowly.

4

CHAPTER 2Determination of Melting

Point and Boiling Point

Fig. 2.1. Sealing one end of the capillary tube.

Sealed capillary