lab manual

PONDICHERRY UNIVERSITY

CHEMISTRY LABORATORY

SYLLABUS

1.DETERMINATION OF TOTAL HARDNESS OF WATER BY EDTA METHOD.

2.ESTIMATION OF MAGNESIUM BY EDTA METHOD.

3.ESTIMATIN OF COPPER IN COPPER SULPHATE SOLUTION.

4.DETERMINATION OF DISSOLVED OXYGEN IN WATER.

5.ESTIMATION OF PERCENTAGE OF ACETIC ACID IN VINEGAR.

6.ESTIMATION OF AVAILABLE CHLORINE IN BLEACHING POWDER.

7.ESTIMATION OF FERROUS BY PERMANGANOMETRY.

8.ESTIMATION OF MIXTURE OF ALKALI.

9.ESTIMATION OF IRON BY COLORIMETRY.

10.ESTIMATION OF CHOLRIDES IN WATER.

11.ESTIMATION OF FERROUS AND FERRIC IRON BY DICHROMETRY.

12.ESTIMATION OF CALCIUM BY POTASSIUM PERMANGANATE.

DEMONSTRATION EXPERIMENTS.

1.DETERMINATION OF COD OF WATER SAMPEL.

2.DETERMINATION OF LEAD BY CONDUCTOMETRY.

3.PERCENTAGE COMPOSITION OF SUGAR SOLUTION BY VISCOMETRY.

1

LIST OF EXPERIMENT.

A. NEUTRALISATION TITRATION

1. ESTIMATION OF MIXTURE OF ALKALI.

2. ESTIMATION OF PERCENTAGE OF ACETIC ACID IN VINEGAR

B. REDOX TITRATION

PERMANGANOMETRY

3. ESTIMATION OF FERROUS BY PERMANGANOMETRY

C. IODOMETRY

4. DETERMINATION OF DISSOLVED OXYGEN IN WATER.

5. ESTIMATION OF AVAILABLE CHLORINE IN BLEACHING POWDER.

6. ESTIMATION OF COPPER IN COPPER SULPHATE SOLUTION.

D. PRECIPITATION TITRATION

ARGENTOMETRY

7. ESTIMATION OF CHOLRIDES IN WATER.

E. COMPLEXOMETRIC TITRATION

EDTA TITRATION

8. DETERMINATION OF TOTAL HARDNESS OF WATER BY EDTA

METHOD.

9. ESTIMATION OF MAGNESIUM BY EDTA METHOD.

F. INSTRUMENTATION EXPERIMENTS

10. ESTIMATION OF IRON BY COLORIMETRY.

11.DETERMINATION OF LEAD BY CONDUCTOMETRY.

12. PERCENTAGE COMPOSITION OF SUGAR SOLUTION BY

VISCOMETRY.

2

INDEX

EXPT.NO DATE NAME OF THE EXPERIMENT SIGNATURE REMARKS

1.

2.

3.

4.

5.

6.

7.

8.

3

9.

GUIDELINES TO BE FOLLOWED IN CHEMISRTY LABORATORY:

The following guideline should be adopted to avoid most of the accidents

occurring in the Chemistry lab.

1. Students should listen carefully the instructions given

during the practical classes.

2. Laboratory coat must be worn at all times during the

laboratory period.

3. Do not perform unauthorized experiments.

4. Record your observation as and when you proceed.

5. Many laboratory chemicals are poisonous. Hence the

students are advised not to taste any chemical or

solution.

6. Read the label carefully before taking a chemical from

its container.

7. Replace the reagent bottles in their respective place

after use.

8. Never pour the reagents back in to the reagent bottle.

9. When diluting concentrated acids, pour the acid slowly

into the water with constant stirring. Never add water

to the acid.

10.Sink is only for draining the liquid .do not throw any

solid material into the sink.

11.Do not use cracked or broken glassware.

4

12.Use tongs or towel to handle hot objects.

13. Spatula should be used to handle chemicals. Never use

your fingers.

14.Any accident or breakage during the experiment work

should be reported to the faculty in charge or lab

instructor immediately.

15.Keep gas and water taps closed when not in use.

16.After completing the experiment .wash every

apparatus, disconnect all electrical connections, keep

the apparatus in proper places and clean your work

table before leaving the laboratory.

17. Submit observation note book and record note book

within a week time.

FUNDAMETALS OF VOLUMETRIC ANALYSIS

Two major methods are available in the analysis of substances are

QUALITATIVE ANALYSIS:

It deals with the analysis of the quality or chemical nature of the substance by determining the

acidic and basic radicals.

QUANTITATIVE ANALSIS:

It enables us to find out the quantity or exact amount of a substance present in a give sample.

Quantitative analysis is classified into two types.

GRAVIMETRIC ANALYSIS:

In this, the quantity of the substance is determined by methods, which make use of direct

weighing.

VOLUMETRIC ANALYSIS:

It is the method of finding out the quantity of the substance from the measurement of volumes

of reacting solution.

5

In volumetric analysis, the concentration of a solution is determined by using another suitable

solution whose concentration is known accurately.

TERMS USED IN VOLUMETRIC ANALYSIS:

TITRATION

The process of determining the strength of an unknown solution (taken in the conical flask) by

allowing it to react with a standard solution (solution of known strength taken in the burette) is known

as titration. The completion of the reaction is monitored by the use of an indicator.

TITRANT

The solution containing a known weight (know concentration) of a substance is called a

titrant.

TITRATE

The solution which contains a substance to be estimated (unknown concentration) is known as

Titrate.

STANDARD SOLUTION

When the exact amount of the substance present in a definite volume of the solution is known

as standard solution.

STANDARD SOLUTION:

The substance which is unaltered in air during weighing is known as primary standard

substance. Solution of known concentration, by weighing a definite amount of primary standard

substance are called standard solution .These primary substances should not be hygroscopic nor

oxidized by air. Eg: Na2CO3, K2Cr2O7 and NaCl.

1. SECONDARY STANDARD:

The substance whose composition is altered is called as secondary standard substance. A

solution of approximate concentration which varies with time is called secondary solution

and its contents of the active substance will be found by comparison against a primary

standard. Eg: NaOH and KMnO4.

Concentration of a solution is expressed in various ways:

6

(a)NORMALITY (N): The normality of a solution is the number of gram equivalent of the solute per

litre of the solution.

No. of gram equivalent of solute

Normality (N) =

Volume of solution in 1000 ml

(b)MOLARITY (M): The molarity of a solution is the number of moles of the solute per litre of the

solution.

No. of moles of solute

Molarity (M) =

Volume of solution in 1000ml

(c)MOLALITY (m): The molality of a solution is the number of moles of the solute per 1000g of

the solvent

No. of moles of solute

Molality (m) =

Mass of solvent in Kg

INDICATOR

It is substance which when added to the titrate, indicator the completion of reaction by

changing its colour at the end point.

END POINT

This is the point in the titration, which indicates the completion of a chemical reaction.

STANDARDISATION

It means determination of the strength of an unknown solution with the help of a standard

solution.

ESTIMATION

To find out the amount of a substance present in a certain volume of the given solution.

SOLUTE

7

The substance, which dissolves into the solution, is called as a solute.

NORMAL SOLUTION (1N SOLUTION)

A normal solution is a solution containing one gram equivalent weight of the solute in one

litre of the solvent.

DECI~NORMAL SOLUTION (N\10 SOLUTION)

A solution containing one tenth of a (1\10) gram equivalent of the solute in one litre of

the solution is known as deci~normal solution.

PRINCIPEL INVOLVED IN VOLUMETRIC ANALYSIS

Volumetric analysis is based on the law of volumetric analysis. When two solutions

completely react with each other, the product of volume and normality of one solution will be equal to

the product of volume and normality of the other solution.

V1N1 = V2N2

V1=Volume of the first solution

N1=Normality of the first solution

V2=Volume of the second solution

N2=Normality of the second solution

IMPORTANT CALCULATION

1. Normality (strength) of a solution=

(Weight of the solute in one litre) \ (Equivalent weight of the solute)

2. Weight of the solute in one litre=

(Equivalent weight of the solute) x (Normality of the solution)

3. Weight of solute present in y ml of the solution=

Equivalent weight of solute x Normality of the solution x (y\1000)

Types of the reaction involved in volumetric analysis

1. Neutralization reaction.

2. Oxidation –Reduction reaction.

8

3. Precipitation titrations.

4. Complexometric titration.

1. NEUTRALIZATION REACTIONS:

The reaction between an acid and base resulting in the formation of salt and water is known

as neutralization reaction.

The acid is titrated against the base or vice versa in the presence of an indicator. The

indicator will have one colour in acid medium and entirely different colour in acid medium and entirely

different colour in basic medium i.e., the colour changes with changes in pH of the solution .

Two types of titration are

ACIDIMETRY: Estimation of amount of acid

ALKALIMETRY: Estimation of amount of an alkali.

Common indicator used is methyl orange, phenolphthalein, methyl red …….

2. OXIDATION~REDUCTION REACTION

They are also called redox reaction i.e., the process of oxidation and reduction takes place

simultaneously. The commonly used oxidising agents are potassium permanganate, potassium

dichromate and the reducing agents are oxalic acid,FAS…. These reaction are class classified into three

types.

a) PERMA

b) PERMAGANOMETRY

Estimation of the substances by using permanganate as an oxidizing agent.

c) DICHROMETRY

Estimation of the substance by using dichromate as an oxidizing agent.

d) IODOMETRY

Estimation of the substance with reducing properties by using liberated iodine.

2. PRECIPITATAION TITRATION

In the precipitation titration , one of the reacting constituent is separated in the form of a

precipitate during the course of titration.

3. COMPLEXOMETRIC TITRATION (EDTA TITRATION)

9

Estimation of the solution involving complex formation by using a complexing agent

EDTA and a complexing indicator Eriochrome black~T.

5. APPARATUS USED IN VOLUMETRIC ANALYSIS

1. BURETTE

2. PIPETTE

3. CONICAL FLASK

4. VOLUMETRIC FLASK (SMF)

5. FUNNEL

6. MEASURING JAR

7. WEIGHING BOTTLE

6. ABBREVATION USED IN VOLUMETRIC ANALYSIS

1. V VOLUME

2. ml MILLI LITRE

3. gm GRAMS

4. N NORMALITY

5. CONC CONCENTRATED

6. dIL DILUTED

7. ppm PARTS PER MILLION

EQUIVALENT WEIGHTS OF SOME INORGANIC SUBSTANCES

SUBSTANCE Eq.WT

NaHCO3 84

Na2C03 53

K2Cr2O7 49.04

Feso4.7H20 278

Feso4.(NH4)2 SO4.6H2O 392.2

Na2S2O3.5H2O 248.2

10

CuSO4. 5H2O 249.7

AgNO3 170

NaCl 58.44

CaCO3 50

FERROUS ION 55.85

COPPER ION 63.54

STRENGTH 0F COMMON ACIDS:

ACID STRENGTH

HCl 12

HNO3 16

H2SO4 36

CH3COOH 17

AMMONIA 14

INDICATORS AND THEIR pH RANGE

INDICATOR pH RANGE ACIDIC BASIC

METHYL ORANGE 3.1~4.4 RED ORANGE

PHENOLPHTALEIN 8.3~10 COLOURLESS RED

TITRATION ~1 STANDARDIZATION OF EDTA

BURETTE SOLUTION EDTA

PIPETTE SOLUTION 20ML OF STANDARD HARD WATER

INDICATOR ERICHROME BLACK~T (EBT)

END POINT COLOUR CHANGE FROM WINE RED TO STEEL

BLUE

ADDITION SOLUTION 2ML OF AMMONI BUFFER SOLUTION

11

STANDARD HARDWATER Vs EDTA

SI.NO Volume of standard

hard water (ml)

Burette Reading

(ml)

Volume of EDTA

(V2 ) ml

Concordant

value ( ml)

Initial Final

1. 20

2. 20

3. 20

Volume of hard water sample = 20ml

Volume of EDTA consumed (V1) =…………ml (titre value)

1ml of the standard hard water contains 1mg of calcium carbonate

20ml of the standard hard water contains 20mg of CaCo3

20ml of standard hard water consumes V1 ml of EDTA

V1 ml of EDTA solution = 20mg of CaCo3

1ml of EDTA solution = (20\ V1)mg of CaCo3 equivalent

= (20\ ……)ml of CaCo3 equivalent

= ……………….mg of CaCo3

Expt.no :

DATE :

ESTIMATION OF TOTAL HARDNESS OF WATER BY EDTA

METHOD

AIM

To estimate total hardness in the give sample of hard water by EDTA method.

CHEMICALS REQUIRED

1.Standard hard water

2.EDTA

12

3.Erichrome black ~T

4.Ammonia buffer solution

PRINCIPLE

The hardness of water is due to dissolved bicarbonate, carbonates (Temporary hardness)

And chlorides,sulphates of calcium and magnesium (permanent hardness).

Ethylene diamine tetra acetic acid (EDTA) is a tetra carboxylic acid. This method is

based upon the fact that EDTA forms remarkable stable complexes with metals,

particularly di and polyvalent metals and it can be represented as,

EDTA dose not dissolve completely

in water and hence its disodium salt is used to estimate the various hardness producing ions

present in the hard water. EDTA is abbreviated as Na2H2Y and its dissociation at pH 10 is,

Na2H2y → H2Y2~ + 2 Na+

EDTA react with Ca and Mg ions forming stable complexes.

Mg2+ + H2Y2~ → Mgy2~+ 2H+

The indicator Erichrome black~T is a tribasic acid dye represented by H3In which dissociate to

different coloured ions at various pH.

TITRATION ~2

ESTIMATION OF TOTAL HATDNESS OF WATER SAMPLE


PIPETTE SOLUTION 20ML OF SAMPLE HARD WATER



BLUE

13



SI.NO Volume of water

sample ( V1 )

(ml)

Burette Reading

(ml)

Volume of EDTA

(V2 ) ml

Concordant

value ( ml)

Initial Final

1.

2.

3.

Volume of hard water sample (V1) = 20ml

Volume of EDTA consumed (V2) =…………ml (titre value)

20ml of the given hard water sample consumes (V2) ml of EDTA

20ml of the given hard water sample contains (20\ V1) × V2 mg of CaCo3

1000ml of given hard water sample contains

= (20\V1) × V2×(100\20) mg of CaCo3

= 1000 × (V2\V1) mg of CaCo3

= 1000 × ……… ml

20

Total hardness of the given sample of hard water =………….ppm

H3In → H2In→ HIn2~→In3~

Red < pH 6> Blue < pH 12> orange

The bivalent blue coloured indicator ion which exists at about pH 10 react with Mg2+, producing red

coloured Mg~ indicator complex.

HIn2~ + Mg2+ → MgHIn

The relative stability of the complexes is as follows.

Ca~EDTA complex> Mg~EDTA> Mg~indicator complex.

So if a drop of indicator is added to hard water sample containing Ca and Mg ions at pH 10, the

Mg~ indicator complex will be formed producing red colour.now to this solution, if EDTA solution is

gradually added it will remove Ca~ions first because Ca~ EDTA complex being more stable. when all

calcium ions are used up, excess EDTA if added will snatch Mg2+ ions from Mg~ indicator complex

14

(because Mg~ EDTA complex is more stable than Mg~ indicator complex) leaving the bivalent indicator

ion free, which being blue in colour will produce blue colour solution. Thus a colour change from red to

blue will indicate the end point.

The overall reaction involved are,

Metal ion + EBT → Metal ions ~EBT weak complex

(Ca2+/ Mg2+ ) (indicator) (Wine red colour)

Metal ions~ EBT + EDTA → Metal ions ~EDTA + EBT

(unstable complex) (wine red colour) (stable complex) (blue colour)

PROCEDURE

Titration 1: standardization of EDTA

A standard hard water solution is prepared in 1ooml volumetric flask.20ml of this solution is

pipetted out into a clean conical flask.2ml of ammonia buffer solution and 2 drops of Eriochrome Black~T indicator

are added and the solution turns wine red in colour.contents of the conical flask are then titrated against EDTA

solution taken in the burette.A colour change from wine red to blue is the end point. The titration is repeated to get

concordant value.

Titration 2: Estimation of Total Hardness of water

The given hard water is made upto the mark in 100ml volumetric flask.

20ml of this solution is pipetted out into a clean conical flask.2ml of ammonia buffer solution and 2 drops of EBT

indicator are added and the solution turns wine red colour.contents of the conical flask are titrated against standard

EDTA solution taken in the burette.A colour change from wine red to blue is the end point. The titration is repeated

for concordant value.From the titre value the total hardness of sample water is determined.

RESULT

The total hardness present in given water sample =…………..ppm.

TITRATION ~1 STANDARDIZATION OF EDTA


PIPETTE SOLUTION 20ML OF ZINC SULPHATE



BLUE


15


SI.NO Volume of Zinc

sulphate (ml)

Burette Reading

(ml)

Volume of EDTA

(V2 ) ml

Concordant

value ( ml)

Initial Final

1. 20

2. 20

3. 20

Volume of Zinc sulphate (V1) = 20ml

Normality of Zinc sulphate (V2) = …………….N

Volume of EDTA (V2) = …………….ml

Normality of EDTA ( N2 ) = ……………N

V1N1 = V2N2

N2 = V1N1

V2

Normality of EDTA = Volume of ZnSO4 × Normality of ZnSO4

Volume of EDTA

N2 =………………?

Expt.no:

Date :

ESTIMATION OF MAGNESIUM BY EDTA METHOD

AIM

To estimate the amount of magnesium present in the whole of the given solution.

CHEMICALS REQUIRED

1. EDTA 2.Magnesium sulphate 3.Zinc sulphate 4.Ammonia buffer solution (NH4Cl+NH4OH)

5. EBT (Indicator)

16

PRINCIPLE

This method is based upon the fact that EDTA forms stable complexes with metals , particularly with di

and poly valent metals . The formula of hydrated disodium salt of the reagent is

It is abbreviated as Na2H2Y and its dissociation at pH 10 is written as

Na2H2y → H2Y2~ + 2 Na+

EDTA reacts with divalent metal ions like Mg2+ and Zn2+ to form stable complexes

H2Y2~ + M2+ → MH2Y

The indicator EBT is a tribasic acid dye represented by H3In and dissociates as follows producing different

coloured ions at various pH values.

H3In → H2In → HIn2~ → In3~

Red < pH 6> Blue < pH 12> orange

The bivalent blue coloured indicator ion which exist at about pH10 react with Mg2+ or Zn2+ producing Mg

~indicator or Zn~indicator complexes which are wine red in colour.

HIn ~ + Mg ++ or Zn2+ → MgHIn or ZnHIn.

TITRATION ~2 ESTIMATION OF MAGNESIUM SULPHATE


PIPETTE SOLUTION 20ML OF MAGNESIUM SULPHATE



BLUE


17

NaOOCH2C

HOOCH2CCH2COOH

CH2COONa

N~CH2~CH2~N .2H20


SI.NO Volume of

Magnesium

sulphate (ml)

Burette Reading

(ml)

Volume of EDTA

(V2 ) ml

Concordant

value ( ml)

Initial Final

1. 20

2. 20

3. 20

Volume of EDTA (V1) = …………..ml

Normality of EDTA (N1) = …………….N

Volume of Magnesium sulphate (V2) = 20ml

Normality of Magnesium sulphate ( N2 ) = ……………N

V1N1 = V2N2

N2 = V1N1

V2

Normality of EDTA = volume of EDTA × Normality of EDTA

volume of Mgs04

N2 =………………N

Amount of magnesium = Normality of magnesium solution × Eq.wt (12.16) × 100\1000

=………………g

The metal~ EDTA complexes are more stable than metal indicator complexes when a solution

containing Zn or Mg~ions is titrated with EDTA in the presence of the indicator, the EDTA first reacts

with free metals~EDTA complex and at the end point the metal is displaced from the metal~ indicator

complex by EDTA leaving the free indicator ion which is blue in colour.Therefore the change from Wine

red to blue is the end point.

PROCEDURE

Titration 1: STANDARDIZATION OF EDTA

18

A standard hard water solution is prepared in 1ooml volumetric flask.20ml of this solution is

pipetted out into a clean conical flask.2ml of ammonia buffer solution and 2 drops of Eriochrome Black~T indicator

are added and the solution turns wine red in colour.contents of the conical flask are then titrated against EDTA

solution taken in the burette. A colour change from wine red to blue is the end point. The titration is repeated to get

concordant value.

Titration 2: ESTIMATION OF MAGNESIUM SULPHATE

The given unknown magnesium sulphate solution is made up to the mark in a clean 100ml SMF.20ml of this

solution is pipetted out in a clean conical flask.5ml of buffer solution (NH4Cl + NH40H) and 1-2 drops of

Eriochrome Black-T indicator is added and the Wine red coloured solution is titrated against EDTA

taken in the burette until the colour changes to blue. The titration is repeated for concordant values.

RESULT

The amount of magnesium present in the whole of the given solution = ………..g

TITRATION 1: STANDARDIZATION OF SODIUM THIOSULPHATE

Burette Solution - Sodium thiosulphate

Pipette Solution - 20ml of standard potassium dichromate

Indicator - Starch solution

End point - Appearance of pale green colour

Additional Solution - 20ml of 2NHCL+10ml of 10%KI

19

Standard K2Cr2O7 Vs Na2S2O3

SI.NO Volume of

K2Cr2O7 solution

(V1)(ml)

Burette Reading

(ml)

Volume of

Na2S2O3 solution

(V2 ) ml

Concordant

value ( ml)

Initial Final

1. 20

2. 20

3. 20

Volume of potassium dichromate solution (V1) = ------------- ml

Normality of potassium dichromate solution (N1)= ------------ N

Volume of sodium thiosulphate solution (V2)= ---------- ml

Normality of sodium thiosulphate solution (N2)= ---------- N

V1N1 = V2N2

N2 = V1N1

V2

Normality of sodium thiosulphate = Volume of K2Cr2O7× Normality of K2Cr2O7

Volume of Na2S2O3

Normality of sodium thiosulphate = ---------------------- N

Expt.No:

Date:

ESTIMATION OF COPPER

AIM:

To estimate the amount of copper present in given brass piece.

CHEMICALS REQUIRED:

20

1. Potassium dichromate

2. Sodium thiosulphate

3. Brass piece

4. Conc.HNO3

5. 10%KI

6. Starch indicator

7. 2NHCL

PRINCIPLE

STANDARDIZATION OF SODIUM THIOSULPHATE

Potassium dichromate oxidizes an acidified solution of KI to an equivalent of iodine.

The iodine liberated is titrated against sodium thiosulphate using starch as indicator.

K2Cr2O7 + 14HCL + 6KI → 8KCL + 2CrCl3 + 7H2O + 3I2

ESTIMATION OF COPPER

The determination of copper is based on iodometric titration. A known quantity of copper ore

is dissolved in conc.HNO3 and the nitrate is removed by fuming with conc.H2SO4

and adjusting the pH by NH4OH. Copper react with KI in acetic acid medium. Copper is precipitated as

cuprous iodide and an equivalent amount of iodine is liberated.

2Cu2+ + 4KI → Cu2Cl2 + 4K+ + I2↑

The liberated iodine is titrated against standard sodium thiosulphate using starch indicator.

2Na2S2O3 + I2 → 2NaI + Na2S4O6

TITRATION :2 ESTIMATION OF COPPER

Burette solution - Sodium thiosulphate

Pipette solution - 20ml of copper solution

Indicator - Starch solution

End point - Appearance of dirty white colour

Additional solution -10ml of acetic acid+ NH3 + 10ml of 10% of KI

21

Eq.Wt. of copper - 63.5

Sodium thiosulphate Vs Copper solution

SI.NO Volume of Copper

Solution(V1) (ml)

Burette Reading

(ml)

Volume of Sodium

Thiosulphate

(V2 ) ml

Concordant

value ( ml)

Initial Final

1. 20

2. 20

3. 20

Volume of sodium thiosulphate solution (V1) = ---------------ml

Normality of sodium thiosulphate solution (N1) = ------------N

Volume of copper solution (V2) = ---------------- ml

Normality of copper solution (N2) = -----------------N

V1N1=V2N2 N2=V1N1/V2

Normality of copper solution = Volume of Na2S2O7×Normality of Na2S2O7

Volume of copper solution

Normality of copper solution = --------------N

PROCEDURE:

TITRATION 1: STANDARDIZATION OF SODIUM THIOSULPHATE

A standard solution of potassium dichromate is prepared in a 100ml volumetric flask .

20ml of potassium dichromate is pipetted out into a clean conical flask. About 20ml of 2N HCL and

10%KI are added and the liberated iodine is titrated against sodium thiosulphate solution taken in the

burette. When the iodine solution becomes pale yellow in colour , 1ml of freshly prepared starch

solution is added and the titration is continued. At the end point, blue colour

22

will suddenly discharge and a pale green colour takes place due to the chromic salt. The titration

are repeated for concordant value. From the titre value, the strength of sodium thiosulphate is

calculated.

TITRATION 2: ESTIMATION OF COPPER

The given copper solution is made upto the mark in a 100ml volumetric flask. 20ml

of the copper solution is pipetted out into a clean conical flask and 1:1NH3 is added drop by drop

till a faint blue colour appears (cupric hydroxide). The alkali destroys the free mineral acid.

Glacial acetic acid is added in drops to make the solution clear. About 10ml of 10%KI is added

and the liberated iodine is titrated against the sodium thiosulphate. When the solution becomes pale

yellow colour, 1ml of freshly prepared starch indicator is added and the titration is continued. At the end

point blue colour suddenly changes to dirty white due to the precipitate of cuprous iodide. The titrations

are repeated for concordant value. From the titre value the amount of copper and hence the percentage

of copper present in the sample is calculated.

RESULT:

Amount of copper present in whole of the given solution= g

Percentage of copper in the sample= %

TITRATION:1 STANDARDIZATION OF SODIUM THIOSULPHATE

Burette solution - Sodium Thiosulphate

Pipette solution - 20ml of standard potassium dichromate

Indicator - 1ml of 1% starch solution


23

Additional solution - 20ml of 2NHCL + 10ml of 10% KI


SI.NO Volume of

K2Cr2O7

Solution(V1) (ml)

Burette Reading

(ml)

Volume of

Na2S2O3 solution

(V2 ) ml

Concordant

value ( ml)

Initial Final

1. 20

2. 20

3. 20

Volume of potassium dichromate solution (V1) =

Normality of potassium dichromate solution (N1) =

Volume of sodium thiosulphate solution (V2) =

Normality of sodium thiosulphate solution (N2) =

V1N1=V2N2 N2= V1N1\V2

Normality of Sodium thiosulphate = Volume of K2Cr2O7 × Normality of K2Cr2O7

Volume of Sodium thiosulphate

Normality of sodium thiosulphate =

Expt.No:

Date:

DETERMINATION OF DISSOLVED OXYGEN IN WATER

BY WINKLER’S METHOD

AIM

24

To determine the dissolved oxygen present in given water sample by Winkler’s method.

CHEMICAL REQUIRED

1. Standard K2Cr2O7 solution

2. Sodium thiosulphate

3. 40%manganous sulphate

4. Alkaline KI solution

5. 1%Starch indicator

6. Conc.H2SO4

PRINCIPLE

STANDARDIZATION OF SODIUM THIOSULPHATE

Potassium dichromate oxidizes an acidified solution of KI to an equivalent amount of iodine. Iodine

liberated is titrated against Na2S2O3 using starch indicator.

K2Cr2O7 + 14HCl + 6KI → 3I2 + 8KCL + 2CrCl3 + 7H2O

ESTIMATION OF DISSOLVED OXYGEN

Oxygen dissolved in water to the extent of 7-9mg\lit at a temperature range of 25-35c. The estimation

of dissolved oxygen is based on the fact that atomic oxygen decomposes potassium iodide liberating free

iodine. This can be titrated against a standard solution of sodium thiosulphate using starch indicator. But

oxygen present in water is in molecular form, its conversion into atomic state is necessary. This is done

by reacting the water sample with manganous hydroxide formed by the reaction of manganous sulphate

with potassium hydroxide.

MnSO4 + 2KOH → Mn (OH)2 + K2SO4

Mn (OH)2 + (O) → MnO(OH)2↓

MnO (OH)2 + 2H2SO4 + 4KI → MnSO4 + 2K2SO4 + 3H2O + 2I2

This liberated iodine is titrated with standard sodium thiosulphate solution.

2Na2S2O3 + I2 →2NaI + 2NaI + Na2S4O6

TITRATION:2 ESTIMATION OF DISSOLVED OXYGEN IN WATER SAMPLE

Burette Solution -Sodium thiosulphate

Pipette solution - 100ml of water sample

Indicator - 1ml of 1%starch solution

End point - Disappearance of blue colour

25

Additional solution -2ml MnSO4+2ml Alkaline KI + Conc.H2SO4

Eq.wt of Oxygen - 8

Sodium thiosulphate Vs Water sample

SI.NO Volume of water

sample (V1) (ml)

Burette Reading

(ml)

Volume of Sodium

thiosulphate

(V2 ) ml

Concordant

value ( ml)

Initial Final

1. 20

2. 20

3. 20

Volume of Sodium thiosulphate (V1) = ----------- ml

Normality of sodium thiosulphate (V2) =---------- ml

Volume of water sample (V2) = ------------ ml

Normality of water sample (N2) =---------- N

V1N1=V2N2

N2=V1N1\V2

Normality of dissolved oxygen= ---------------------N

Amount of dissolved oxygen present in one litre of water sample

=Normality of dissolved oxygen ×Eq.wt of oxygen (8) ×1000

= N×8×1000

Amount of dissolved oxygen = ppm.

PROCEDURE:

TITRATION:1 STANDARDIZATION OF SODIUM THIOSULPHATE

A standard solution of Potassium dichromate is prepared in a 100ml volumetric

flask.20ml of Potassium dichromate solution is pipetted out into a clean conical flask. About 20ml of 2N

HCl and 10ml of 10%KI are added. The liberated iodine is titrated against sodium thiosulphate solution

taken in the burette. When the iodine solution becomes straw yellow in colour, 1ml of freshly prepared

26

starch indicator is added and the titration is continued carefully. At the end point, blue colour will

suddenly discharge and a pale green colour takes place due to the chromic salt. The titrations are

repeated to get concordant value. From the titre value, the strength of sodium thiosulphate is calculated.

TITRATION 2: ESTIMATION OF DISSOLVED OXYGEN The given water sample is taken in a 250ml reagent bottle leaving 10ml space. To this,

2ml of manganous sulphate solution and 2ml of alkaline KI solution are added and precipitate of

manganous hydroxide will be formed. The bottle is shaken well to facilitate the reaction on Mn (OH) 2

precipitate with the dissolved oxygen present in the water sample. When all the dissolved oxygen in

water has reacted with Mn (OH) 2, it gives a brown precipitate of basic manganic hydroxide. Now Conc.H2SO4

is added drop by drop to dissolve the precipitate till yellow solution of iodine is obtained.

100ml of this iodine solution is taken into a clean conical flask and titrated against sodium

thiosulphate solution using starch indicator. Disappearance of blue colour is the end point. From the titre value the

strength of dissolved oxygen is calculated and from this the amount of dissolved oxygen in the water sample is

calculated.

RESULT:

The amount of dissolved Oxygen in the given water sample = ---------------- ppm.

TITRATION:1 STANDARDIZATION OF NaOH

Burette solution - Sodium Hydroxide (NaOH)

Pipette solution - 20ml of oxalic acid

Indicator - Phenolphthalein

End point - Appearance of pale pink colour

27


SI.NO Volume of

Oxalic acid

Solution(V1) (ml)

Burette Reading

(ml)

Volume of NaOH

solution

(V2 ) ml

Concordant

value ( ml)

Initial Final

1. 20

2. 20

3. 20

Volume of oxalic acid solution (V1) = 20ml

Normality of oxalic acid solution (N1) = ------------ N

Volume of NaOH solution (V2) = ---------------ml

Normality of NaOH solution (N2) = -----------N

V1N1=V2N2

N2= V1N1\V2

Normality of NaOH = Volume of Oxalic acid × Normality of Oxalic acid

Volume of NaOH

Normality of NaOH ( N2 )= --------------------- N

Expt.No:

Date:

ESTIMATION OF VINEGAR

AIM

To estimate the amount of acetic acid is in the given vinegar.

28

CHEMICALS REQUIRED:

1. Oxalic acid

2. NaOH

3. Phenolphthalein

4. Vinegar

PRINCIPLE

A known weight of vinegar is diluted with water and the percentage of acetic acid is

found by titrating it against standard sodium hydroxide solution using phenolphthalein as indicator.

CH3COOH + NaOH CH3COONa + H2O

Oxalic acid reacts with sodium hydroxide to give sodium oxalate and water and hence used as primary

standard to standardize sodium hydroxide.

H2C2O4 + 2NaOH Na2C2O4 + 2H2O

PROCEDURE:

TITRATION-1: STANDARDIZATION OF NaOH

A standard solution of oxalic acid is prepared in a clean conical flask .20ml of oxalic acid is

pipetted out in a clean conical flask and one drop of phenolphthalein indicator is added. The colourless

solution is titrated against NaOH from the burette. The end point is the appearance of Pale pink colour.

The titration is repeated for concordant values.

TITRATION:2 ESTIMATION OF VINEGAR

Burette solution - Sodium Hydroxide (NaOH)

Pipette solution - 20ml of vinegar

Indicator - Phenolphthalein

29

End point - Appearance of pale pink colour

Standard NaOH Vs vinegar

SI.NO Volume of Vinegar

Solution

(ml)

Burette Reading

(ml)

Volume of NaOH

solution

ml

Concordant

value ( ml)

Initial Final

1. 20

2. 20

3. 20

Volume of NaOH solution (V1) = --------------- ml

Normality of NaOH solution (N1) = --------------- N

Volume of Vinegar solution (V2) = 20ml

Normality of Vinegar solution (N2) =--------?

V1N1=V2N2

N2= V1N1\V2

Normality of CH3COOH in vinegar = Volume of NaOH × Normality of NaOH

Volume of Vinegar

N2 = ----------------- N

Amount of acetic acid present in the

Whole of the given solution = Normality of Acetic acid × Eq.wt (60) × 1OO

1000

TITRATION-2 ESTIMATION OF VINEGAR

By using a weighing bottle an exactly known weight of the given vinegar sample is

transferred into a clean 100ml SMF and made up the mark. 20ml of this solution is pipetted out into a

conical flask and 2 drop of phenolphthalein indicator is added. The solution is titrated against NaOH

30

from the burette. The end point is the appearance of pale pink colour. The titration is repeated for

concordant values.

RESULT:

The Amount of Acetic acid present in the whole of the give solution is = ------------------------ g.

TITRATION: 1 STANDARDIZATION OF SODIUM THIOSULPHATE

Burette solution - Sodium Thiosulphate

Pipette solution - 20ml of standard potassium dichromate

31



Additional solution - 20ml of 2NHCL + 10ml of 10% KI


SI.NO Volume of

K2Cr2O7

Solution(V1) (ml)

Burette Reading

(ml)

Volume of

Na2S2O3 solution

(V2 ) ml

Concordant

value ( ml)

Initial Final

1. 20

2. 20

3. 20

Volume of potassium dichromate solution (V1) = 20ml

Normality of potassium dichromate solution (N1) = -----------N

Volume of sodium thiosulphate solution (V2) = -----------ml

Normality of sodium thiosulphate solution (N2) = ----------N

V1N1=V2N2

N2= V1N1\V2

Normality of Sodium thiosulphate = Volume of K2Cr2O7 × Normality of K2Cr2O7

Volume of Sodium thiosulphate

Normality of sodium thiosulphate (N2) = ------------------N

Expt.No:

Date:

ESTIMATION OF AVAILABLE CHOLRINE IN BLEACHING POWDER

32

AIM:

To estimate the amount of available chlorine in given sample bleaching powder.

CHEMICALS REQUIRED:

1. Potassium dichromate 4.2N HCl 7.Starch indicator

2. Sodium thiosulphate 5.2N Acetic acid

3. Bleaching Powder 6.10% KI

PRINCIPLE:

The commercial sample of bleaching Powder is a mixture of calcium hydroxide, calcium

chloride, calcium hypochlorite Ca(OCl2) and Calcium chlorate Ca(ClO3)2 . When bleaching Powder is

treated with dilute acid , chlorine is evolved. The chlorine liberated is known as available chlorine.

Estimation of available chlorine is useful in determining the quality of bleaching Powder. Commercial

sample has 36- 38% of available chlorine.

CaCl (OCl) + 2CH3COOH (CH3COO) 2Ca + H2O + Cl2

Bleaching powder

A known volume of a solution of bleaching powder is treated with excess of potassium iodide and

acidified with acetic acid.

CaOCl2 +2KI +2CH3COOH I2 + CaCl2 + 2CH3COOK

The iodine liberated is titrated against sodium thiosulphate solution using starch indicator

I2 + 2Na2S2O3 Na2S406 + 2NaI

From the amount of liberated iodine , the equivalent of Cl2 and hence the available chlorine in

the sample is calculated

TITRATION: 2 ESTIMATION OF AVAILABLE CHLORINE

Burette solution - Sodium Thiosulphate solution

Pipette solution - 20ml of bleaching powder solution

33



Additional solution - 20ml of dil.Acetic acid+ 10ml of 10% KI

Eq.Wt.of chlorine - 35.45

Standard Na2S2O3 Vs Bleaching powder solution

SI.NO Volume of

Bleaching powder

Solution(V1) (ml)

Burette Reading

(ml)

Volume of

Na2S2O3 solution

(V2 ) ml

Concordant

value ( ml)

Initial Final

1. 20

2. 20

3. 20

Volume of sodium thiosulphate solution (V1) = -----------ml

Normality of sodium thiosulphate solution (N1) = -----------N

Volume of Bleaching powder Solution (V2) = 20ml

Normality of chlorine (N2) = ----------N

V1N1=V2N2

N2= V1N1\V2

Normality of chlorine N2 = ---------------N

Amount of chlorine = Normality of chlorine × Eq.Wt of chlorine × 100

1000

= -------------N × 35.45 × 100/1000

Amount of chlorine present = -----------g.

PROCEDURE:

TITRATION: 1 STANDARDIZATION OF SODIUM THIOSULPHATE

34

A standard solution of Potassium dichromate is prepared in a 100ml volumetric

flask.20ml of Potassium dichromate solution is pipetted out into a clean conical flask. About 20ml of 2N

HCl and 10ml of 10%KI are added. The liberated iodine is titrated against sodium thiosulphate solution

taken in the burette. When the iodine solution becomes straw yellow in colour, 1ml of freshly prepared

starch indicator is added and the titration is continued carefully. At the end point, blue colour will

suddenly discharge and a pale green colour takes place due to the chromic salt. The titrations are

repeated to get concordant value. From the titre value, the strength of sodium thiosulphate is calculated.

TITRATION: 2 ESTIMATION OF AVAILABLE CHOLRINE

Make up the given solution of bleaching powder up to the mark in 1OOml

volumetric flask. Pipette out 20ml of this solution into a clean conical flask. Add about 10ml of 10% KI

solution and 10ml of 2N acetic acid. The solution turns dark brown in colour due to the liberated

iodine .Titrate the liberated iodine against sodium thiosulphate.When the solution become straw yellow,

1ml of freshly prepared starch indicator is added and the titration is continued. End point is the

disappearance of blue colour. Repeat the titration for concordant values. From the titre value the

chlorine liberated and hence its amount in the sample is calculated.

RESULT:

Amount of available chlorine present in whole of the given sample of bleaching Powder

solution = --------------------g.

35

lab manual

Documents

Transcript of lab manual