LAB MANUAL · PDF file · 2017-11-11Preparation of soyabean milk and its comparison with the natural milk with respect to curd formation, effect of temperature, etc. Study of the

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PrincipalPathfinder Global School

Haryana

New Saraswati House (India) Pvt. Ltd.NEW DELHI-110002 (INDIA)

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Reprint 2016

ISBN: 978-81-7335-551-6

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LM Chemistry-12

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SYLLABUSEvaluation Scheme for Examination Marks

Volumetric Analysis 10 MarksSalt Analysis 8 MarksContent Based Experiment 6 MarksClass Record, Project Work and Viva 6 Marks

Total 30 Marks

60 PeriodsMicro-chemical methods are available for several of the practical experiments. Wherever possible, such techniques should be used.

A. Surface Chemistry(a) Preparation of one lyophilic and one lyophobic sol.

Lyophilic sol—starch, egg albumin and gum.Lyophobic sol—aluminium hydroxide, ferric hydroxide, arsenious sulphide.

(b) Dialysis of sol—prepared in (a) above(c) Study of the role of emulsifying agents in stabilizing the emulsions of different oils.

B. Chemical Kinetics(a) Effect of concentration and temperature on the rate of reaction between sodium thiosulphate

and hydrochloric acid.(b) Study of reaction rates of any one of the following:

(i) Reaction of iodide ion with hydrogen peroxide at room temperature using differentconcentration of iodide ions.

(ii) Reaction between potassium iodate, KIO3 and sodium sulphite (Na2SO3) usingstarch solution as indicator (clock reaction).

C. ThermochemistryAny one of the following experiments

(i) Enthalpy of dissolution of copper sulphate or potassium nitrate.(ii) Enthalpy of neutralization of strong acid (HCl) and strong base (NaOH).

(iii) Determination of enthalpy change during interaction (Hydrogen bond formation) betweenacetone and chloroform.

D. ElectrochemistryVariation of cell potential in Zn/Zn2+||Cu2+/Cu with change in concentration of electrolytes(CuSO4 or ZnSO4) at room temperature.

E. Chromatography(i) Separation of pigments from extracts of leaves and flowers by paper chromatography and

determination of Rf values.(ii) Separation of constituents present in an inorganic mixture containing two cations only

(constituents having large difference in Rf values to be provided).F. Preparation of Inorganic Compounds

(i) Preparation of double salt of ferrous ammonium sulphate or potash alum.(ii) Preparation of potassium ferric oxalate.

G. Preparation of Organic CompoundsPreparation of any two of the following compounds

(i) Acetanilide(ii) Di-benzal acetone

(iii) p-Nitroacetanilide(iv) Aniline yellow or 2 - Naphthol aniline dye

H. Test for the functional groups present in organic compounds:Unsaturation, alcoholic, phenolic, aldehydic, ketonic, carboxylic and amino (primary) groups.

I. Characteristic test of carbohydrates, fats and proteins in pure samples and their detectionin given foodstuffs.

J. Determination of concentration/molarity of KMnO4 solution by titrating it against astandard solution of:

(i) Oxalic acid,(ii) Ferrous ammonium sulphate

(Students will be required to prepare standard solutions by weighing themselves).

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K. Qualitative analysisDetermination of one cation and one anion in a given salt.

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

Anions — CO32–, S2–, SO3

2–, SO42–, NO2

–, NO3–, Cl–, Br–, I–, PO4

3–, C2O42–, CH3COO–

(Note: Insoluble salts excluded.)

Project

Scientific investigations involving laboratory testing and collecting information from other sources.

A Few Suggested Projects● Study of presence of oxalate ions in guava fruit at different stages of ripening.● Study of quantity of casein present in different samples of milk.

● Preparation of soyabean milk and its comparison with the natural milk with respect to curd formation, effect oftemperature, etc.

● Study of the effect of potassium sulphite as food preservative under various conditions (temperature, concentration, timeetc.).

● Study of digestion of starch by salivary amylase and, effect of pH and temperature on it.● Comparative study of the rate of fermentation of following materials: wheat flour, gram flour, potato juice, carrot juice

etc.

● Extraction of essential oils present in Saunf (aniseed), Ajwain (carum), Illaichi (cardamom).● Study of common food adulterants in fat, oil, butter, sugar, turmeric powder, chilli powder and pepper.

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

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CONTENTSS.No. Experiments Page No.

CHEMISTRY LABORATORY 7–141. SURFACE CHEMISTRY 15–22

1.1 To prepare colloidal solution of starch 151.2 To prepare colloidal solution of egg albumin 151.3 To prepare colloidal solution of gum 161.4 To prepare colloidal solution of ferric hydroxide 161.5 To prepare a colloidal solution of aluminium hydroxide 171.6 To prepare a colloidal solution of arsenous sulphide (As2S3) 171.7 To purify the colloidal solution containing sodium chloride or other electrolytes as an impurity by dialysis 181.8 To study the effectiveness of different oils in forming emulsions and to study the role of emulsifying

agents in stabilizing the emulsions of different oils 20

2. CHEMICAL KINETICS 23–282.1 To study the effect of concentration on the rate of reaction between sodium thiosulphate

and hydrochloric acid 232.2 To study the effect of temperature on the rate of reaction between sodium thiosulphate

and HCl. You are provided with M/20 solutions of the two substances 242.3 To study the rate of reaction of iodide ion with hydrogen peroxide at room temperature

using different concentration of iodide ions 262.4 The study the reaction rate between potassium iodate (KIO)3 and sodium sulphite (Na2SO3)

using starch solution as indicator 28

3. THERMOCHEMISTRY: DETERMINATION OF ENTHALPY OF SOLUTIONAND ENTHALPY OF NEUTRALIZATION 29–35

3.1 To determine enthalpy of solution of potassium nitrate 303.2 To determine enthalpy of solution of solid copper sulphate (CuSO4.5H2O) in water at room temperature. 323.3 To determine enthalpy of neutralization of the reaction between HCl and NaOH 333.4 To determine the enthalpy change during interaction (hydrogen bond formation)

between acetone and chloroform 34

4. ELECTROCHEMISTRY: VARIATION OF CELL POTENTIAL WITHCHANGE IN CONCENTRATION OF ELECTROLYTE 36–39

4.1 To study the variation of cell potential in Zn/Zn2+||Cu2+/Cu with change inconcentration of electrolytes (CuSO4 or ZnSO4) at room temperature 36

5. CHROMATOGRAPHY 40–435.1 To separate the coloured components present in the mixture of red and blue

inks by ascending paper chromatography and find their Rf values 405.2 To separate the coloured components (pigments) present in the given extract

of leaves and flowers by ascending paper chromatography and find their Rf values 405.3 To separate constituents present in an inorganic mixture containing Pb2+ and Cd2+ ions 41

6. PREPARATION OF INORGANIC COMPOUNDS 44–496.1 Preparation of double salt of ferrous ammonium sulphate (Mohr’s salt)

from ferrous sulphate and ammonium sulphate 446.2 To prepare crystals of potash alum from K2SO4 and Al2(SO4)3 456.3 To prepare crystals of potassium ferric oxalate

[potassium trioxalato ferrate (III)] K3[Fe (C2O4)3]. 3H2O 46

7. PREPARATION OF ACETANILIDE, DIBENZAL ACETONE,p-NITRO ACETANILIDE AND βββββ-NAPHTHOL ANILINE DYE 50–53

7.1 To prepare acetanilide in the laboratory 507.2 To prepare dibenzal acetone in laboratory 507.3 To prepare p-nitro acetanilide 517.4 To prepare β-naphthol aniline dye 51

8. TEST FOR FUNCTIONAL GROUPS IN ORGANIC COMPOUNDS 54–608.1 To test the functional groups of organic compounds 54

(A) To test presence of unsaturation 54(B) To test the presence of alcoholic group 54(C) To test the presence of phenolic group 55(D) To test the presence of aldehydic and ketonic group 56

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(E) To test the presence of carboxylic group 57(F) To test the presence of keto group 57(G) To test the presence of amino group 58

9. STUDY OF CARBOHYDRATES, FATS AND PROTEINS 61–649.1 To study simple reactions of carbohydrates, fats, proteins and

detection of their presence in given foodstuffs 619.2 To identify carbohydrates, fats and proteins in foodstuffs 62

10. VOLUMETRIC ANALYSIS (REDOX TITRATION) 65–8310.1(a) Setting of a chemical balance and preparation of standard solution of oxalic acid and Mohr’s salt 6510.1(b) To prepare standard solution of oxalic acid and Mohr’s salt. 68

10.2 You are provided with standard solution of KMnO4 (M/100). Using this solution findout the molarity and strength of ferrous ammonium sulphate (Mohr’s salt) solution 69

10.3(a) A solution of ferrous ammonium sulphate containing 17.0 g of salt in one litre is providedto you. Using this solution determine the concentration of KMnO4 in gL– 1 in the givensolution and calculate its percentage purity if ‘X’ grams of it have been dissolved per litre 71

10.3(b) Determine the equivalent mass and number of water of crystallisation molecules in the sampleof Mohr’s salt, FeSO4.(NH4)2SO4.xH2O contains 19.6 g L–1 provided M/100 KMnO4 72

10.3(c) You are provided with a partially oxidised sample of ferrous sulphate (FeSO4.7H2O) crystals.Prepare a solution by dissolving 14.0 g of these crystals per litre and determine the precentageoxidation of the given sample. 74

10.4 You are provided with a standard solution of M/40 of oxalic acid. With its help determine themolarity and strength of KMnO4 solution 75

10.5 You are provided with M/100 KMnO4 solution. With its help, find out the percentagepurity of impure sample of oxalic acid, x grams of which have been dissolved per litre 76

10.6 A dealer has supplied a hydrated sample of oxalic acid containing ‘x’ water molecules.Find out volumetrically the percentage of water in the sample of oxalic acid with thehelp of M/20 KMnO4 solution 78

11. QUALITATIVE INORGANIC ANALYSIS 84–106(A) Preliminary Tests 84(B) Analysis of Anions: Test for dil. H2SO4 group, Conc. H2SO4 group 88(C) Analysis of Cations: Test for NH4

+ (Zero group) 93(D) Group Analysis 94

INVESTIGATORY PROJECTS 107–1701. Study of oxalate ion content in guava 1072. Determination of the quantity of casein present in different samples of milk 1093. Preparation of soya bean milk and its comparison with natural milk with respect to curd formation,

effect of temperature, etc. 1104. To study the effect of potassium metabisulphite as food preservative under various conditions. 1125. To study digestion of starch by salivary amylase and effect of pH and temperature on it. 1136. Comparative study of the rate of fermentation of various food materials. 1147. Extraction of essential oil present in Saunf (aniseed), Ajwain (carum) and Illaichi (cardamom). 1178. Study of common food adulterant in fat oil, butter, suggar, turmeric powder, chilli powder and pepper. 1189. Analysis of soil samples 119

10. Preparation and application of some pesticides. 12311. To extract nicotine from tobacco-based Pan-masala. 12512. Analysis of radish 12713. To find the amount of chlorine in different samples of water. 13014. 1. To calculate the Van’t Hoff’s factor of different salts using water as the solvent. 132

2. To find if the molecules of salt associate or dissociate in its solution with water.15. To analyse the presence of carbohydrates, proteins and fats in various fruits and vegetables. 14216. To study photography and to prepare contact prints. 14617. To prepare indicators using onion peel and beetroot. 14818. To find the variation of conductance with temperature in electrolytes. 14919. Study the content of ascorbic acid, i.e., vitamin C in citrus fruits. 15220. To analyse coconut water for the presence of anions, cations and foodstuffs present in it. 15821. Preparation of potash alum from aluminium scraps. 16222. To prepare hard plastic (Urea-formaldehyde resin) 16423. Effect of temperature on stability of coordination compounds. 16524. To prove that decomposition of hydrogen peroxide is a first order reaction. 168

Appendix I-II 171–175

Log Tables 176–179

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Chemistry is science of experiments. Scientific concepts can be easily understood by performing experiments. Laboratory experimentsare being influenced by the modern techniques and electronic devices and there is adequate blending of information and communicationtechnology and practical laboratory experiments.

A chemistry laboratory is that place where experiments in chemistry are performed. A student need to understand the properway of working in chemistry laboratory. A student must know the proper use of each equipment and the precautions to be observedwhile working in the laboratory.

A brief introduction of important features of every chemistry laboratory, some safety and laboratory rules are as follows:1. Lab Coat. A student must bring white lab coat made of cotton up to proper length (below knees).2. Observation Notebook. A student must bring a notebook for writing brief notes about experiment, observations, inferences.

Write experiment number, date of performing the experiment, aim of experiment and materials required before writingobservations.

3. Demonstration Table. The table in front of blackboard (white board is also being used these days) for giving instructionsand demonstration of experiments by teacher is called demonstration table. The students should be very attentive duringdemonstration and keep on noting down important points especially precautions so that experiment can be performedsuccessfully and safely.

4. Student’s Working Table. A number of wooden or iron or concrete tables are provided for working. Each table is dividedinto seats, one seat is allotted to each student for performing experiments. Student’s must maintain their seat neat and clean.Each seat is provided with following fixtures and materials.(a) Reagent Shelf. A shelf is made in front of seat, made up of wooden or iron, on which reagents which are very

frequently used are placed, e.g., concentrated and dilute HCl, HNO3, HCl, bases like NaOH, NH4OH and other reagentslike BaCl2, (NH4)2CO3, lead acetate [Pb(CH3COO)2] etc.

(b) Sinks and Water Taps. A sink and a water tap is provided between the shelves for the ready supply of water. Open awater tap carefully and gradually and close the tap, when it is not required. The water in the tap is under high pressure.Do not open the tap fully otherwise it will spoil your working seat and your clothes.Waste liquids are thrown into the sink. Do not throw any insoluble solid material like filter papers, broken glassapparatus etc. into the sink these which will block the drain. Throw them into dustbin carefully. Throw broken pieces ofglass very carefully. Do not touch sharp edge of glass.

(c) Gas Taps. These are fitted on the seats for supply of gas. These days, mostly LPG gas is used for this purpose. Open thegas tap only when it is required and keep it close when not in use. Do not keep the burner lighted when not in use.

(d) Dustbin. Each laboratory must have one or more dustbins depending upon size of laboratory and number of studentsworking. It is meant for throwing solid waste materials, filter paper, litmus and pH papers, broken glass materials etc.Burning papers and materials must be extinguished before throwing them into dustbin.

(e) Side Shelves. Side shelves mostly made up of wooden or iron are fitted on the walls of the laboratory. Reagents andchemicals which are less frequently used are placed in these shelves. Reagents, on the side shelves are usually placed inalphabetical order. No reagent should be carried to the seat because other students also need them. It should be placedback at its proper place, properly stoppered after use.

(f) Fume Cupboard. Every laboratory should have at least one fume cupboard in the corner of the laboratory. Allexperiments giving out poisonous gases or vapours are performed in this cupboard. It is a small chamber having asliding glass wall and a chimney fitted with an exhaust fan at the top. Put on the exhaust fan before starting theexperiment into it.If fume cupboard is not available, perform such experiments near the window away from the nose and mouth and keepthe test tube out of window till fumes stops.

(g) Exhaust Fan. Switch on the exhaust fans and open all the windows and both the doors if there are fumes in thelaboratory. If still there is suffocation or breathing problem, inform the teacher and go out in fresh air till the fumes areremoved from the lab with the help of exhaust fan. Switch off exhaust fans, when not required.

Balance Room. It is small room attached to each laboratory. A number of chemical balances are kept for weighing thesubstances in this room. Do not touch or disturb the balances when not required.

Use balance only after teacher has given instruction how to use it. Ask your teacher if you have any doubt.

Chemistry Laboratory

Chemistry Laboratory

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Saraswati Lab Manual Chemistry–XII8

INSTRUCTIONS TO WORK IN A LABORATORY1. A student must have laboratory coat before entering the chemistry lab from safety point of view.2. A student must have a practical notebook (previous practical written) which should be kept on teacher’s table and not on

student’s working table so that it does not get spoiled.3. A student must have observation notebook for instruction, a pen, pencil, geometry box, platinum wire, fractional weights, as

per requirement.4. Always come prepared for the experiment. Ask for all minute details from the teacher when instructions are being given.

Listen the instructions very carefully and note down important points.5. After the instructions, collect the apparatus from the laboratory assistant in a systematic manner.6. Clean the apparatus thoroughly before use.7. Do the experiments as per instruction given carefully with full alertness. Do not mix the reagents unnecessarily, it may lead

to explosion.8. Do your experiments honestly and if there is any error, discuss with your teacher. Record your observations in your

observation notebook and do not write on pieces of paper or at the back of practical file.9. Plan your work so that it can be completed on time. Do not delay otherwise you will miss next class.

10. Use the proper amount of reagents carefully. Excess of reagents wherever not required should not be used. If excess ofreagent is required, then use it slowly and carefully.

11. Handle the glass apparatus carefully. In case of breakage, report it to your teacher at once.12. Dispose off all waste liquids, solutions in the sink and allow continuous flow of water till the sink is clean.13. Keep your seat clean. If an acid or any other chemical is spilled wash it off and wipe it with a cloth.14. Clean the apparatus and return it to laboratory assistant or keep it at proper place as instructed.15. In case of injury or accident report it to the teacher immediately.16. Wash your hands with soap after the experiment.17. Do not talk unnecessarily in the lab or talk very slowly.18. Do not push each other, move very carefully.19. Never lose patience. If experiment is not successful, try to find out the cause and repeat by following correct procedure and

discuss with your teacher.20. Do not leave half the experiment otherwise you have to do it all over again. Better plan it out properly and take permission

of your teacher if little extra time is needed.

OBSERVATION COPY AND PRACTICAL FILEAll the practicals done in the laboratory are recorded in observation copy during experiment and in practical file at home.

An accurate and proper record of experimental results and conclusions is an indispensable part of scientific work.Keep the following important points in mind while writing practicals:1. Cover your practical file properly with brown cover or any other cover as instructed by teacher and write your name, class,

section, roll no. on the cover. It will be better if it is covered with plastic sheet also.2. Write you name, class and section in the place given on the first page of your practical file.3. Write the aim of experiment along with the date of carrying out experiment, page number in the index regularly.4. Write experiment number, aim of experiment, date of carrying out experiment, materials required, basic principles involved,

procedure, precautions and result on ruled page (right hand side).5. Write only in ink neatly and carefully.6. Use a soft pencil for the diagram if any and make observation table, chemical equation (if any), calculations and result on

white page (left hand side).7. Start writing every new experiment on a fresh page.8. Write procedure point wise.9. Theory and basic principle of experiment should be given in precise manner.

10. Record data accurately in a tabular or other form as per instructions.11. Never cook the data, always work honestly, since there is always a limit to accuracy of the measurement.12. Do not take average in volumetric analysis rather take concordant readings.

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13. Do not tear pages from notebook.14. No overwriting is allowed in practical file.15. Think before you write and write practicals regularly and not all on one day. Do not write experiments late at night, when

you are feeling sleepy.16. Use only blue ink and not red, green, black etc. Do not change the ink or pen in between the experiment.17. Get you copy checked regularly. Make the corrections if required and do not repeat the mistakes. Keep your copy safe, away

from water, chemicals.

SAFETY RULES1. Do not perform unauthorised experiments.2. Never work in the lab alone.3. Report all accidents immediately to your teacher.4. If vapours generated are toxic, use a fume hood.5. Wear a chemical splash goggles and resistant gloves.6. Wear a chemical resistant apron.7. Tie back long hair.8. Do not wear loose sleeves.9. Do not wear shorts.

10. Do not wear sandals.11. Do not wear contact lenses.12. No food or beverages.13. No gum chewing.14. Do not leave experiments unattended.15. Know the location of the exits, safety showers, eye wash, fire blankets, fire extinguishers and telephone.16. No running.17. Keep aisles clear.18. Extinguish burners when away from desk.

COMMON LABORATORY APPARATUS

Chemistry Laboratory

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Saraswati Lab Manual Chemistry–XII10

Common Laboratory apparatus used in Chemistry Laboratory

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The students can work in laboratory and do experiments if they are familiar with the apparatus commonly used in thelaboratory. Some such apparatus are shown in Fig 1.1 and described as follows:

1. Test tube. It is glass tube closed at one end. It is used for carrying out reactions and various tests.2. Centrifuging tube. It is tringular at the bottom and used for obtaining precipitate if centrifuging machine is available. It will

save time required for filtration.3. Boiling tube. It is bigger in size than the test tube for carrying out various tests where strong heating of substances is

required. It is made up of hard glass or pyrex glass.4. Test tube brush. It is used for cleaning test tube.5. Gas detector. It is U-shaped tube as shown in diagram and is very useful for detecting a gas evolved.6. Funnel stand. It is a stand having circular clamp to hold the funnel. If it is not available, tripod stand can be used.7. Funnel. It is cone shaped wide glass tube drawn into long narrow neck. It is used for filtration purpose or for pouring liquids

into narrow mouthed reagent bottles.8. Wash bottle. It is made of plastic or glass as shown in diagram. It has jet through which water can be used under pressure

for washing or dissolving purposes. Distilled water should be used for purpose of dissolving.9. Tripod stand. It is made of cast iron and is used as a support for heating beakers, porcelain dishes etc. which is placed over

a wire gauze placed over tripod stand. It can also be used as funnel stand.10. Wire gauze. It is a gauze made of fine iron wires fitted with a thin asbestos sheet in the centre. It helps in heating the glass

apparatus evenly and, therefore, reduces the chances of breakage.11. China dish or Porcelain dish. It is shallow bowl of porcelain as shown in figure. It is used for heating or evaporation of

substances. It should also be heated on wire gauze.12. Glass rod. It is a cylindrical thin stick of glass. It is used for stirring solutions or mixing of substances.13. Blue glass. It is blue coloured glass strip so as to see the colour of flame produced by inorganic salts.14. Watch glass. It is made of glass having concave shape. It is used for weighing accurate amount of solids with the help of

chemical balance.15. Platinum wire. It is used for performing flame tests in qualitative analysis.16. Charcoal block. It is made up of charcoal. It is used for charcoal cavity test.17. Mouth blow pipe. It is made up of iron. It is used to direct the flame towards the cavity in the charcoal cavity test.18. Charcoal borer. It is made up of iron. It is used to make cavity in charcoal.19. Beaker. It is flat bottomed cylinderical vessel made up of glass with a beak. These are available in various capacities

generally 50 ml, 100 ml, 250 ml, 500 ml and 1000 ml. Beaker is used for storing, mixing and heating of substances.These days plastic beakers are also being used but they should not be heated. Oxidizing agents and organic solvents cannotbe stored in them.

20. Glass tube. It is hollow thin cylindrical tube made of glass. It is used for transporting liquids or gases.21. Round bottom flask. It is made up of glass having round bottom and a long narrow neck. It is used in the experiments

where reaction requires heating of substances.22. Flat bottom flask. It is a made up of glass having a round body which is flat at the bottom and a long narrow neck. It is used

for storing solution or carrying out reactions in cold.23. Conical flask. It is made up of glass having conical shape. It is usually used for carrying out titrations. It can be heated if

made up of corning or borosil glass.24. Measuring cylinder. It is graduated glass cylinder used for the approximate measurement of volume of liquids. They are

available in capacity of 10 ml, 50 ml, 100 ml and 250 ml.25. Air condenser. It is about 50 cm long glass tube with a wider mouth at one end. It is used for condensing vapours to liquid,

but only for those substances whose boiling points are more than 150 °C.26. Water condenser. It is long glass tube surrounded by outer glass jacket which has two openings, one is inlet which is

connected to the tap and outlet through which water goes out to the sink with the help of rubber pipe. It is used forcondensing vapours into liquid form.

27. Dropper. It is a short glass tube drawn into a fine jet at one end and fixed with a rubber teeth on the other. It is used forpouring of solution in drops.

28. Test tube holder. It is for holding the test tube during heating. It is made up of metal strip or thick wire. It must be usedwhile heating.

29. Iron stand. It is long iron rod mounted on a heavy iron base. It is used to hold, support or suspend such apparatus whichwould fall otherwise. A ring or clamp with boss of iron or brass is used to fix the apparatus with the iron rod of the stand.

Chemistry Laboratory

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Saraswati Lab Manual Chemistry–XII12

30. Triangular file. It is long triangular shape rod made of hard alloy steel having a series of ridges on its surface. It is used forreducing or smoothing surfaces of glass, rubber corks, wood, metals etc.

31. Sand bath. It is flat plate of iron containing sand. It is used when heating is to be done slowly and uniformly.32. Water bath. It is copper vessel and is used for heating at low temperature. It limits the temperature to the boiling point of

water. If an oil is used in place of water, it is called oil bath which is used for heating at higher temperature.33. Test tube stand. It is made of wood or plastic and is used for keeping test tubes. There are wooden or plastic pegs fitted on

the stand and are used to keep the clean test tube upside down.34. Spatula. It is a sort of spoon made of plastic, nickel or steel. It is used to transfer powdered or solid substances.35. Centrifuging. It is used for separating precipitate. It is used to save time required for filtration.36. Pair of tongs. It is used to hold hot china dish. It is made up of steel or iron.37. Burette. It is made up of glass. It is long graduated tube from 0 to 50 having least count 0.1 ml having a knob at the bottom

so as to regulate the flow of liquid. It is used in titration.38. Pipette. It is used to measure fixed volume of solution by sucking and controlling with the help of finger up to the mark. It is

available in capacities of 10 ml, 20 ml and 25 ml.39. Weighing bottle. It is small bottle made up of glass having a lid. It is used for weighing small amount of liquids.40. Spirit lamp. It is used for heating purposes at the places where gas burners are not available. It can be used in class room for

demonstration purposes. It is made up of glass or iron, having a cotton wick dipped in spirit. It cannot be used for strongheating. It should be handled with care.

CLEANING OF GLASS APPARATUSThe glass apparatus is generally cleaned by washing powder such as ‘Vim’. A suitable brush is used for cleaning purposes. It shouldbe then thoroughly washed with water and finally rinsed with distilled water. If the apparatus is dirty or greesy, it may be rinsed withchromic acid [5g of K2Cr2O7 + 100 ml of H2SO4(conc.)] or conc. HNO3. It is very corrosive, therefore, should not be touched.

BURNERSThese use combustible gases such as LPG as a fuel. Bunsen burner is simplest and most commonly used. Its construction andworking is explained as follows:

(i) Base. It is made of cast iron, keeps the burner in a stable and upright position.(ii) Gas inlet pipe. It fits horizontally into the side of a base and can be connected to the gas tap through a rubber tube.

(iii) Nipple. It is made up of brass rod and has a fine pin hole running through it. It is screwed to the base at the bottom andcarries a burner tube over it.

(iv) Burner tube. It is metallic tube with two opposite air holes near its lower end. It is screwed on the nipple and carries the airregulator.

(v) Air regulator. It is metallic ring with two holes opposite to each other corresponding to the holes of the burner tube. It slipsover the burner tube and regulates the supply of air.

WORKINGThe mixture of air and combustible gas burns at the top with a flame. There are two types of flame produced:

(i) Non-luminous or oxidising flame. Non-luminous is hottest flame, blue in colour and not noisy. It needs required amount ofair for complete combustion of fuel. The air flow can be adjusted with the help of air regulator.

(ii) Luminous flame or reducing flame. It is yellow in colour and smoky. It is produced due to incomplete combustion of fuel.When air holes are closed or open to very little extent or the nipple is not clean, we get luminous flame. It is used in charcoalcavity test. It should not be used for heating because it has lower temperature and there will be black deposite on apparatuswhich are unburnt carbon particles.

ADVANTAGES OF BURNERS1. The size of flame can be regulated by regulating the supply of gas from the gas tap, i.e., open the gas tap partially.2. It does not produce smoke.

PRECAUTIONS1. Sometimes, the gas begins to burn at the nipple. This is called striking back of the burner. In such a case, close the gas

supply first, then reduce the amount of air supply.

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13

2. Sometimes noisy flame is produced which is not very hot and stable. In such cases, close the airholes to such an extent thatthe flame becomes steady, noiseless and non-luminous.

3. Never allow the chemicals to go inside the burner tube. It will block the nipple.

FIRST AID EMERGENCY TREATMENTS IN THE LABORATORYAccidents in the laboratory may occur due to carelessness or due to improper handling. It may occur by chance also. In case of anaccident, do not lose presence of mind. Report to the teacher at once and follow the first aid emergency treatments given below:

Type of Accidents Treatment

1. Burns: (i) Burn by heat Apply Burnol.(ii) Burns causing blisters Apply Burnol as earliest as possible.(iii) Acid burns Wash under free water continuously until irritation stops. If burning persists, wipe

with cotton and apply Burnol.(iv) Alkali burns Wash freely with water. Dry the skin and apply Burnol.(v) Bromine burns Wash with 2% solution of NH3 and then rub glycerine. Also apply Burnol after

sometime.(vi) Sodium burns Remove the sodium piece sticking to skin with forceps. Wash thoroughly with water,

then with 10% acetic acid and then with water again. Cover with a piece of cottonsoaked in ethanol.

2. Cuts:(i) Minor cuts Allow to bleed for a few seconds. Remove the glass piece, if any, carefully. Apply

spirit and cover it with a piece of cotton.(ii) Serious cuts Apply pressure above the cut to stop bleeding. Report to the teacher and consult the

doctor.

3. Eye Accidents: (i) Acid in eye Wash thoroughly with water.(ii) Foreign particle in the eye Do not rub the eye. Wash the eye with water. Use clean handkerchief to remove the

particle.(iii) Alkali in eye Wash thoroughly with water, then wash with 10% solution of boric acid.(iv) Soreness in the eye Put drop of olive oil and keep the eye closed for sometime.

4. Poisons:(i) Poisons not swallowed Spit out immediately. Wash the mouth with water.

(ii) Acid swallowed Drink a lot of water.(iii) Alkalies swallowed Drink a lot of water. Drink a glass of lemon or orange juice.(iv) Salts of heavy metal Take milk or white of an egg.(v) Arsenic or Take one spoon of common salt or ZnSO4 with warm water.

mercury compounds(vi) Inhalation of gases like Cl2, Go in open air.

SO2, Br2 etc. causingsuffocation.

5. Fire:(i) Clothes catch fire Do not run. Wrap with blanket. Lie down and roll.

(ii) Beaker or flask containing Cover the beaker or flask with damp cloth.inflammable liquid catchesfire.

(iii) Some wooden materials Throw sand or water.catches fire.

(iv) Spirit or oil catches fire. Throw sand and sodium bicarbonate if there is small scale fire. Use fire extinguisherif fire is on large scale.

(v) Electrical part catches fire. Switch off immediately and throw sand or NaHCO3. Do not throw water.

Chemistry Laboratory

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Saraswati Lab Manual Chemistry–XII14

VIVA VOCE QUESTIONSQ1. When would you use lab coat?

Ans. Lab coat is used while doing experiments in chemistry laboratory.Q2. Which colour lab coat should be used?

Ans. White.Q3. Why?

Ans. It does not absorb heat.Q4. When will you switch on exhaust fan?

Ans. When there are fumes in the lab, we switch on exhaust fan.Q5. When would you make use of fume cupboard?

Ans. It is used while performing experiments in which poisonous gases or vapours are evolved.Q6. Should we taste chemicals in the laboratory?

Ans. No, chemicals should never be tasted. They may be poisonous and thus harmful.Q7. What will you do if your skin comes in contact with acid?

Ans. Wash it with running water continuously, then apply Burnol.Q8. What will you do if you inhale a poisonous gas?

Ans. Go out in open air.Q9. What will you do if your clothes catch fire?

Ans. Lie down on the floor and roll.Q10. What will you do if you swallow dilute alkali?Ans. Drink lot of water. Drink lemon juice or orange juice.Q11. If you get acid in eye, what will you do?Ans. Wash it thoroughly with running water and then wash it with 10% solution of boric acid and use clean handkerchief.Q12. Which type of flame is hottest?Ans. Non-luminous.Q13. Why?Ans. It is because it is formed by complete combustion of fuel.Q14. What is the colour of luminous flame?Ans. Yellow.Q15. Why?Ans. It is due to presence of unburnt carbon particles which absorb heat and glow.Q16. On which page of practical file will you write observations?Ans. Observations must be written on white page in pencil.Q17. Can we heat beaker or china dish directly on flame?Ans. No, it should be heated on wire gauze.Q18. How do we prepare dilute H2SO4?Ans. We add acid to water very slowly with constant cooling.Q19. Why should we cool NH3 bottles before opening?Ans. NH3 is liquid at high pressure. It should be cooled so as to reduce the pressure, otherwise, it may burst.Q20. Can we touch conc. H2SO4?Ans. No, we should not touch conc. H2SO4. It is corrosive.

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Saraswati Lab Manual Chemistry Class-XII

Publisher : SChand Publications ISBN : 9788173355516 Author : R. P. Manchanda

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