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LUCKNOW PUBLIC SCHOOL, SOUTH CITY HOLIDAY HOMEWORK

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LUCKNOW PUBLIC SCHOOL

SOUTH CITY A-BLOCK

PRACTICAL WRITING SKILLS

FOR CLASS XII

SUBJECT-CHEMISTRY


SALT ANALYSIS

Tests for acid radicals:

Salt or mixture is treated with dil. 42SOH

Acid Radical Observations Confirmatory test

23CO (carbonate) Brisk effervescence

with evolution of

colourless and

odourless gas.

Gas turns lime water milky but milkiness disappears on

passing gas in excess,

22424232 COOHSONaSOHCONa ;

OHCaCOCOOHCa 2milky

32 waterlime

2)( ;

soluble23223 )(HCOCaCOOHCaCO

2S (sulphide) Smell of rotten

eggs SH2( smell)

on heating

Gas turn lead acetate paper black

Sodium carbonate extract *)(SE + sodium nitroprusside –

purple colour, 422422 SONaSHSOHSNa ;

COOHCHPbSPbCOOCHSH 3(black)

232 2)( ;

(purple)idenitropruss sodium

])([])([ 54522 NOSCNFeNaNOCNFeNaSNa

COOCH3

(acetate)

Solution gives

smell of vinegar

Aq. Solution + neutral 3FeCl blood red colour

NaClCOOCHFeFeClCOONaCH 3)(3(red)

33neutral

33

Salt or mixture is treated with conc. 42SOH

Cl (chloride) Colourless

pungent gas giving

white fumes with

aq. OHNH4

(i)Add 2MnO in the same test tube and heat–pale green 2Cl

gas

(ii)S.E.+ 33 AgNOHNO solution –white ppt. soluble in

aq. 3NH

(iii)Chromyl chloride test

3NO (nitrate) Brown pungent

fumes intensified

by the addition of

Cu- turnings.

(i)S.E.+ 33 AgNOHNO yellow ppt. insoluble in aq.

3NH

(ii)Ring test

Specific test in solution:

Sulphate : S.E. add dil. (to decompose 23CO until reaction ceases). Add 2BaCl solution. White ppt.

insoluble in conc. 3HNO , NaClBaSONaSOBaCl 2 ppt.white

442


Chemical Reactions involved in the tests of Acidic Radicals

Carbonate:

Gas turns lime water milky but milkiness disappears on passing gas in excess,

22424232 COOHSONaSOHCONa ;

OHCaCOCOOHCa 2milky

32 waterlime

2)( ;

soluble23223 )(HCOCaCOOHCaCO

Sulphide:

Gas turns lead acetate paper black

422422 SONaSHSOHSNa ;

COOHCHPbSPbCOOCHSH 3(black)

232 2)( ;

Sodium carbonate extract *)(SE + sodium nitroprusside – purple colour,

(purple)idenitropruss sodium

])([])([ 54522 NOSCNFeNaNOCNFeNaSNa

Chloride:

(i)Add 2MnO in the same test tube and heat–pale green 2Cl gas

HClKHSOSOHKCl 442conc. ; fumes) white(43 ClNHNHHCl

OHClMnClMnOHCl 2222 24

(ii)S.E.+ 33 AgNOHNO solution –white ppt. soluble in aq. 3NH

3 3

white ppt.

KCl AgNO AgCl KNO ; soluble

233 ])([2. ClNHAgNHaqAgCl

(iii) Chromyl- chloride test : Chloride + heat

H conc.)solid( 42722 SOOCrK reddish brown vapours

of chromyl-chloride ).( 22ClCrO Pass these vapours into ,NaOH when yellow 42CrONa solution is formed. On

adding COOHCH3 and 23 )( COOCH Pb, yellow ppt. of lead chromate )( 4PbCrO is formed.

HClKHSOSOHKCl

442conc. ;

OHCrOKHSOSOHOCrK 234conc.

42722 222

OHClCrOHClCrO 2223 22 ;

OHNaClCrONaNaOHClCrO 24222 224

COONaCHPbCrOPbCOOCHCrONa 3 ppt.yellow

42342 2)(


Nitrate:

34423 HNONaHSOSOHNaNO

fumes brown

2223 244 OHONOHNO ;

OHNONOCuHNOCu 22233 22)(4

Ring test : To water extract (all 3NO are water soluble) add freshly prepared 4FeSO solution and then conc.

42SOH carefully by the side of the test- tube. A dark brown ring of 24

252 ])([ SONOOHFe at the interface

between the two liquids is formed.

34423 222 HNONaHSOSOHNaNO ;

OHNOSOFeSOHSOFeHNO 23424243 42)(3362

OHSONOOHFeNOSOOHFe 224

252462 ])([])([

Tests for basic radicals : Analysis of Basic Radicals

Group Group reagent Basic radical Composition and colour of the precipitate

Zero NaOH 4NH Ammonia gas is evolved

I Dilute HCl Ag 2Pb 2Hg

white:HgCl

white:PbCl

white:

2

2

AgCl

HCl dilute cold

insouble

Chloride

II SH2 in presence of

dilute HCl

2Hg 2Pb 3Bi

2

3

3

2

2

Sn

Sb

As

Cd

Cu

yellow:SnS

brown: SnS

orange:Sb

yellow:As

yellow: CdS

black: CuS

black:Bi

black:PbS

black:

2

32

32

32

S

S

S

HgS

HCl dilute

in insoluble

Sulphides

III OHNH4 in presence of

ClNH4

3

3

3

Al

Cr

Fe

white:Al(OH

green:Cr(OH)

brownreddish

:)(

3

3

3OHFe

OH4NH

in insoluble are Hydroxides

IV

OH

SH

4

2

NH

of presencein

2

2

2

2

Ni

Co

Mn

Zn

black: NiS

black:CoS

buff:MnS

whitegreenish

:ZnS

OH4NH

in insoluble are Sulphides

V

OH

CONH

4

324

NH

of presence

in )(

2

2

2

Ca

Sr

Ba

insoluble are Carbonates

white:CaCO

white:SrCO

white:

3

3

3

BaCO

VI 4NaHPO 2Mg White:)( 44 PONHMg


Chemical reactions involved in the tests of Basic Radicals

Zero Group

NH 4 (ammonium) : The substance (salt or mixture) when heated with NaOH solution evolves ammonia.

OHNHNaClNaOHClNH 232

When a rod dipped in HCl is brought on the mouth of the test tube, white fumes of ammonia chloride are

formed, fumes White43 ClNHHClNH

To the aqueous solution of ammonium salt when Nessler’s reagent is added, brown coloured precipitate is

formed.

OHKClKI

I

O

NH

Hg

Hg

KOHClNHHgIK 2

ppt.)(Brown basesMillon'of Iodide

2

442 3742

Group I :

When dil. HCl is added to original solution, insoluble chlorides of lead, silver, mercurous mercury are

precipitated.

3223 22)( HNOPbClHClNHPb ; 33 HNOAgClHClAgNO

3223 22)( HNOHgClHClNOHg

Pb2+ (lead)

(i) 2PbCl is soluble in hot water and on cooling white crystals are again formed.

(ii) The solution of 2PbCl gives a yellow precipitate with potassium chromate solution which is insoluble

in acetic acid but soluble in sodium hydroxide.

KClPbCrOCrOKPbCl 2 ppt.yellow

4422 ;

(iii) The solution of 2PbCl forms a yellow precipitate with potassium iodide solution.

KClPbIKIPbCl 22.pptYellow

22

Hg 22 (mercurous)

(i) 22ClHg turns black with OHNH4 , OHClNHClNHHgHgOHNHClHg 242422 2

Black

)(2

(ii) The black residue dissolves in aqua-regia forming mercuric chloride.

ClOHNOClHNOHCl 223 23 ;

222 426)(2 NHClHgClClClNHHg

22 HgClClHg


Group II : When hydrogen sulphide is passed in acidified solution, the radicals of second group are

precipitated as sulphides.

Pb2+ (lead)

In case the sulphide dissolves in dilute ,3HNO a small part of the solution is taken. Dilute 42SOH is

added. If lead is present, a white precipitate of lead sulphate appears,

3 ppt.)(White

44223 2)( HNOPbSOSOHNOPb

In absence of lead, the remaining solution is made alkaline by the addition of excess of .4OHNH

Bismuth forms a white precipitate of ,)( 3OHBi & Copper forms a deep blue coloured solution while Cadmium

forms a colourless soluble complex,

ppt.White

3)(3)( 343433 NONHOHBiOHNHNOBi ;

solution) blue(deep

nitratecupric e Tetrammin

;4)(])([4)( 22343423 OHNONHCuOHNHNOCu

solution) s(colourles

nitrate cadmium e Tetrammin

4)(])([4)( 22343423 OHNONHCdOHNHNOCd

Cu2+ (copper) : Blue coloured solution is acidified with acetic acid. When potassium ferrocyanide is added a

chocolate coloured precipitate is formed,

442332343 4)(4)()( COONHCHNOCuCOOHCHNONHCu

ppt.Chocolate

4)([])([)(2 3626423 KNOCNFeCuCNFeKNOCu

Cd2+ (cadmium) : SH2 is passed through colourless solution. The appearance of yellow precipitate confirms

the presence of cadmium, 3 ppt.Yellow

3422343 2)()( NHNONHCdSSHNONHCd

Group IIB : In case the precipitate dissolves in yellow ammonium sulphide, the tests of the radicals arsenic,

antimony and tin are performed. The sulphide is treated with concentrated hydrochloric acid. Antimony and

tin sulphide dissolve while arsenic sulphide remains insoluble.

As3+ (arsenic) : The insoluble sulphide is treated with concentrated nitric acid which is then heated with

ammonium molybdate. Yellow precipitate of ammonium arsenomolybdate is formed.

acidArsenic

2243352 5210210 SOHNOAsOHHNOSAs

ppt.Yellow

122112.)(21)(12 2343434342443 OHNONHMoOAsONHHNOMoONHAsOH


Group III : Hydroxides are precipitated on addition of excess of ammonium hydroxide in presence of

ammonium chloride.

ClNHOHAlOHNHAlCl 4 ppt.Gelatinous

343 3)(3 ;

ClNHOHFeOHNHFeCl 4 ppt.red Brownish343 3)(3

Fe3+ (iron) : The brownish red precipitate dissolves in dilute HCl. The solution is divided into two parts.

Part I : ])([ 64 CNFeK solution is added which forms deep blue solution or precipitate.

OHFeClHClOHFe 233 33)( ;

KClCNFeFeCNFeKFeCl 12])([])([34 bluePrussian

364643

Part II : Addition of potassium thiocyanate solution gives a blood red colouration.

KClCNSFeKCNSFeCl 3)(3colour red Blood

33

Al3+(aluminium) : The gelatinous precipitate dissolves in NaOH ,

OHNaAlONaOHOHAl 2Soluble

23 2)(

The solution is boiled with ammonium chloride when 3)(OHAl is again formed.

2 4 2 3 3NaAlO +NH Cl+H O Al(OH) +NaCl+NH

Group IV : On passing SH2 through the filtrate of the third group, sulphides of fourth group are precipitated.

NiS and CoS are black and insoluble in concentrated HCl

while MnS (buff coloured), ZnS (colourless) are soluble in conc. HCl.

Zn2+ (zinc) : The sulphide dissolves in HCl.

SHZnClHClZnS 222

When the solution is treated with ,NaOH first a white precipitate appears which dissolves in excess of NaOH

NaClOHZnNaOHZnCl 2)(2 ppt.White

22 ; OHZnONaNaOHOHZn 2(Soluble)

222 22)(

On passing SH2 , white precipitate of zinc sulphide is formed NaOHZnSSHZnONa 2 ppt.White

222

Ni2+ (nickel) and Co2+ (cobalt)

The black precipitate is dissolved in aqua- regia.

OHSNONiClHNOHClNis 223 2322263

OHSNOCoClHNOHClCoS 223 4323263

The solution is evaporated to dryness and residue extracted with dilute HCl. It is divided into three parts.

Part I : Add OHNH4 (excess) and dimethyl glyoxime. A rosy red precipitate appears, if nickel is present,


OHClNH

CHC

CHC

OH

N

N

O

Ni

O

N

N

OH

CCH

CCH

OHNH

NOHCCH

NOHCCH

NiCl 24

3

3

3

3

4

3

3

2 22|

|

|

|2|2

Part II : Add COOHCH3 in excess and .2KNO The appearance of yellow precipitate confirms the

presence of cobalt.

2332 HNOCOOKCHCOOHCHKNO ; KClNOCoKNOCoCl 2)(2 2222

OHNONOCoHNONOCo 232222 )(2)( ; ])([3)( 623232 NOCoKKNONOCo

Group V : Ammonium carbonate precipitates V group radicals in the form of carbonates are soluble in acetic

acid.

OHCOBaCOOCHCOOHCHBaCO 222333 )(2

OHCOSrCOOCHCOOHCHSrCO 222333 )(2

OHCOCaCOOCHCOOHCHCaCO 222333 )(2

Ba2+ (barium) : Barium chromate is insoluble and precipitated by the addition of potassium

chromate solution, COOKCHBaCrOCrOKCOOCHBa 344223 2)(

Sr2+ (Strontium) : Strontium sulphate is insoluble and precipitated by the addition of ammonium

sulphate solution, 43 ppt.White

442423 2)()( COONHCHSrSOSONHCOOCHSr

Ca2+ (calcium) : Calcium oxalate is insoluble and precipitated by the addition of ammonium oxalate.

43 ppt.White

42422423 2)()( COONHCHOCaCOCNHCOOCHCa

Group VI : In the filtrate of V group, some quantity of ammonium oxalate is added as to remove CaBa, and

Sr completely from the solution. The clear solution is concentrated and made alkaline with .4OHNH

Disodium hydrogen phosphate is now added, a white precipitate is formed.

ppt.)(White

phosphateammonium Megnesium

2)( 2444422 OHNaClPONHMgOHNHHPONaMgCl


Inorganic salt

+ dil. HCl

filter

white residue

(indicates presence of I group)

Pb+2

filtrate

if no ppt. is observed

pass H2S

ppt.

ppt.

ppt.

ppt.

filtrate

filtrate

filtrate

filtrate

(indicates presence of III group)

(indicates presence of II group)

Pb+2,Cu+2,Cd+2


(i) boil off H2S(ii) add small amount of conc. HNO3 & boil(iii) add NH4Cl (pinch) & then NH4OH(excess)

Al+3, Fe+3

filter

filter

pass H2S

(indicates presence of IV group)Zn+2,Co+2,Mn+2,Ni+2

(i) boil off H2S(ii) add NH4Cl (pinch) & then (NH4)2CO3

(indicates presence of V group)Ba+2,Sr+2,Ca+2

(indicates presence of VI group)

Group Analysis of Basic Radicals

Zero gp. :- heat the salt with a little amount of NaOH, if ammoniacal smell is observed then it indicates presence of Zero Gp. i.e. NH4+ ion.




Mg+2


Some Sample Experiments on Salt Analysis

EXPERIMENT-1

Aim: - To determine the presence of one acidic & one basic radical in the given inorganic salt.

Apparatus:-

Salt characteristics:-

1. Physical appearance:- 2. Colour:- 3. Odour:- 4. Solubility:-

Analysis of acidic radical:

Experiment Observation Inference

Test for 23CO

Preliminary test:-

Salt + dil. HCl

Brisk effervescence is observed due

to evolution of CO2 gas

23CO suspected

Confirmatory test for the

suspected acidic radical:- The

gas is passed in lime water

Lime water turns milky 23CO confirmed

Analysis of basic radical:

Experiment & Observation Inference

Zero gp.:-

Preliminary test :-NH4

+ salt + alkali (NaOH or

KOH) + heat . Smell of ammonia is evolved

Indicates the presence of

Zero group

Confirmatory test:- Take a cotton plug with a drop

of Nessler’s reagent on it + ammonia gas

It turns brown.

NH4

+ confirmed

RESULT: The given salt contains:

Acidic Radical: 23CO

Basic Radical: NH4

+


EXPERIMENT-2


Apparatus:-





Test for 24SO

Preliminary & Confirmatory

test for the suspected acidic

radical:-

test:-Salt + dil. HCl + BaCl2

White ppt. due to formation of

BaSO4 which is insoluble in conc.

HNO3

24SO confirmed



Zero gp.:-



KOH) + heat .

Smell of ammonia is evolved


Zero gp.



It turns brown.

NH4

+ confirmed


Acidic Radical: 24SO

Basic Radical: NH4

+


EXPERIMENT-3


Apparatus:-





Test for COOCH3

Preliminary test:-

Salt + H2O (few drops) + oxalic

acid. rub the paste

Smell of vinegar is observed



COOCH3 suspected


suspected acidic radical:-

Salt + dil. HCl + neutral FeCl3

solution

Buff coloured ppt. due to

formation of ferric acetate is

observed

COOCH3 confirmed



Zero gp.:-



KOH) + heat

Smell of ammonia is evolved


Zero gp.



It turns brown.

NH4

+ confirmed


Acidic Radical: COOCH3

Basic Radical: NH4

+


EXPERIMENT-4


Apparatus:-





Test for COOCH3

Preliminary test:-

Salt + H2O (few drops) + oxalic

acid. rub the paste

Smell of vinegar is observed



COOCH3 suspected



Salt + dil. HCl + neutral FeCl3

solution

Buff coloured ppt. due to

formation of ferric acetate is

observed

COOCH3 confirmed



Zero gp.:-



KOH) + heat

No smell of ammonia is evolved

Indicates the absence of

Zero gp.

Salt + dil. HCl white residue is obtained Indicates the presence of

I gp.

I gp. :- Confirmatory test for Pb+2:- dissolve the white

residue obtained in hot water. Divide it in two parts

To I part: - add KI solution a yellow ppt. is obtained

To II part: - add K2CrO

4 solution a yellow ppt. is

obtained

Pb+2

confirmed


Acidic Radical: COOCH3

Basic Radical: Pb+2


EXPERIMENT-5


Apparatus:-





Test for 3NO

Preliminary test:-

Salt + conc. H2SO

4 + Cu turnings

+ heat

Dark brown fumes due to

formation of NO2 evolved

3NO suspected



Salt + dil. H2SO

4 + freshly

prepared FeSO4 solution + conc.

H2SO

4 is added across the walls of

the test tube slowly

A dark brown ring is formed at the

junction of the layers of the acid

and the solution

3NO confirmed



Zero gp.:-



KOH) + heat


Indicates the absence of Zero gp.

Salt + dil. HCl white residue is obtained Indicates the presence of I gp.

I gp. :- Confirmatory test for Pb+2:- dissolve the white residue obtained in hot water. Divide it in two parts

To I part: - add KI solution a yellow ppt. is obtained

To II part: - add K2CrO

4 solution a yellow ppt. is

obtained

Pb+2

confirmed


Acidic Radical: 3NO

Basic Radical: Pb+2


EXPERIMENT-6


Apparatus:-





Test for 23CO

Preliminary test:-

Salt + dil. HCl



23CO suspected







Zero gp.:-



KOH) + heat .



Zero gp.

I gp. :- Salt + dil. HCl :- No residue was obtained. Indicates the absence of

I gp.

H2S gas is passed to this solution

Yellow Precipitate was obtained


II gp.

II gp. :- Confirmatory test for Cd+2:-

Dissolve the white ppt. in dil. HCl.

Add few drops of K4[Fe(CN)

6] a bluish white ppt. is

obtained

Cd+2

Confirmed



Basic Radical: Cd+2


EXPERIMENT-7 Aim: - To determine the presence of one acidic & one basic radical in the given inorganic salt. Apparatus:- Salt characteristics:-




Test for 24SO



radical:-




HNO3

24SO confirmed



Zero gp.:-



KOH) + heat



Zero gp.

I gp. :- Salt + dil. HCl :- No residue was obtained. Indicates the absence of

I gp.

H2S gas is passed to this solution

Black Precipitate was obtained


II gp.

II gp. :- Confirmatory test for Cu+2:-

Dissolve the ppt. in 50% HNO3. Boil off H2S gas. Cool

and then add NH4OH in excess to the first part, Deep

blue colouration is observed

Cu+2

Confirmed

Acidify the deep blue solution with acetic acid and then

add potassium ferrocyanide. Chocolate brown ppt. is

formed

Cu+2

Confirmed



Basic Radical: Cu+2


EXPERIMENT-8


Apparatus:-


1. Physical appearance:-

2. Colour:-

3. Odour:-

4. Solubility:-



Test for 24SO



radical:-




HNO3

24SO confirmed



Zero gp.:-



KOH) + heat



I gp. :- Salt + dil. HCl :- No residue was obtained. Indicates the absence of gp. I

II gp. :- H2S gas is passed to this solution

No precipitate was obtained

Indicates the absence of gp. II

Add NH4Cl (in pinch) + NH4OH to this solution when a white gelatinous floating precipitate is obtained

Indicates the presence of gp. III

III gp. :- Confirmatory test for Al+3:-

Dissolve the white ppt. in dil. HCl.

Add few drops of blue litmus solution + then add NH

4OH till blue colour develops. Blue ppt. floating in

the colourless solution

Al+3

Confirmed



Basic Radical: Al+3


EXPERIMENT-9

Aim: - To determine the presence of one acidic & one basic radical in the given inorganic salt. Apparatus:- Salt characteristics:-




Test for 23CO

Preliminary test:-

Salt + dil. HCl



23CO suspected







Zero gp.:-


+ salt + alkali (NaOH or KOH)

+ heat .



Zero gp

I gp. :- Salt + dil. HCl: - No residue was obtained. Indicates the absence of

I gp.

II gp. :- H2S gas is passed to this solution



II gp.

III gp. :- Add NH4Cl (in pinch) + NH4OH to this solution.



III gp.

H2S gas is passed to this solution white precipitate

was obtained


IV gp.

IV gp. :- Dissolve the ppt. in HCl.

When the solution is treated with ,NaOH first a

white precipitate appears which dissolves in excess

of NaOH

On passing SH2 , white precipitate is re-formed

Zn+2 is present



Basic Radical: Zn+2


EXPERIMENT-10


Apparatus:-





Test for 23CO

Preliminary test:-

Salt + dil. HCl



23CO suspected







Zero gp.:-



+ heat No smell of ammonia is evolved


I gp. :- Salt + dil. HCl: - No residue was obtained. Indicates the absence of I gp.

II gp. :- H2S gas is passed to this solution No precipitate was obtained

Indicates the absence of II gp

III gp. :- Add NH4Cl (in pinch) + NH4OH to this solution. No precipitate was obtained

Indicates the absence of III gp

IV gp. :- H2S gas is passed to this solution No precipitate was obtained

Indicates the absence of IV gp.

V gp. :- Boil off H2S Add NH4Cl (in pinch) + NH4OH to this solution + Add (NH4)2CO3 White ppt. is observed

Indicates the presence of V gp.

The precipitate is dissolved in hot acetic acid solution. To the solution K2CrO4 solution is added

Formation of yellow ppt. confirms the presence of Ba+2 ions.



Basic Radical: Ba+2


EXPERIMENT-11


Apparatus:-





Test for 23CO

Preliminary test:- Salt + dil. HCl

Brisk effervescence is observed due to evolution of CO

2 gas

23CO suspected

Confirmatory test for the suspected acidic radical:- The gas is passed in lime water




Zero gp.:-







Indicates the absence of II gp.


Indicates the absence of III gp.





The precipitate is dissolved in hot acetic acid solution. To the solution (NH4)2SO4 solution is added

Formation of yellow ppt. confirms the presence of Sr+2 ions.



Basic Radical: Sr+2


EXPERIMENT-12


Apparatus:-





Test for 23CO

Preliminary test:-

Salt + dil. HCl



23CO suspected







Zero gp.:-







Indicates the absence of II gp.


Indicates the absence of III gp.





The precipitate is dissolved in hot acetic acid solution. To the solution (NH4)2C2O4 solution is added

Formation of yellow ppt. confirms the presence of Ca+2 ions.



Basic Radical: Ca+2


ORGANIC FUNCTIONAL GROUP ANALYSIS

EXPERIMENT-13

Aim:- To identify the functional group in the given organic compound[CH3COOH]

Apparatus:-

Procedure:-


Test for COOH group :-

Preliminary test:-

Compound + pH paper

Pink colouration is observed

—COOH group

suspected


suspected functional group:-

Compound + NaHCO3 solution



—COOH group

confirmed

Result :- The given organic compound contains the …………………….. functional group

EXPERIMENT-14

Aim:- To identify the functional group in the given organic compound[C2H5OH]

Apparatus:-

Procedure:-


Test for OH group :-

Preliminary test:- Compound +

pH paper

No significant colour change is

observed

—OH group

suspected


suspected functional group:-


No effervescence is observed due


—OH group

suspected


suspected functional group :-

Compound + ceric ammonium

nitrate soln

Pink colouration is observed —OH group

confirmed



EXPERIMENT-15

Aim:- To identify the functional group in the given organic compound[Phenol]

Apparatus:-

Procedure:-


Test for phenolic OH group :-

Preliminary test:-

Compound + pH paper

Significant colour change is

observed

Phenolic —OH

group suspected




No effervescence is observed due


Phenolic —OH

group suspected



Compound + + neutral FeCl3

solution

Violet colouration is observed Phenolic —OH

group confirmed


EXPERIMENT-16

Test for acetone [Preparation of iodoform]

Aim:- To identify the functional group in the given organic compound

Apparatus:-


Test for acetone:-[preparation of iodoform]



In a test tube take some compound

+ one or two drops of NaOH

solution + iodine solution. Keep

the test tube in the water bath.

Leave it for some time

Formation of yellow ppt [i.e.

formation of iodoform]

Acetone is present



EXPERIMENT-17

Aim:- To identify the functional group in the given organic compound

Apparatus:-

By Tollen’s test:-


Test Observation Inference

Oxidation by Tollen’s reagent (silver mirror test) Tollen’s reagent: - it is an ammoniacal solution of AgNO3.

Sample is dissolved in water and to it 5 ml of Tollen’s reagent is added and then heated on water bath.

Aldehydes on reaction with Tollen’s reagent get oxidized to carboxylic acids thereby reducing the Tollen’s reagent to metallic silver. RCHO + 2 [Ag(NH3)2]

+ + 3OH- RCOO- + 2Ag + 2H2O + 4NH3 (silver mirror)

Aldehydes gives a +ve test with Tollen’s reagent.


EXPERIMENT-18

PREPARATION OF AZO- DYE

1. Take 10 ml of aniline in a 50 ml beaker.

2. Dissolve it in excess of HCl.

3. Add NaNO2 solution to it.

4. Cool this mixture in a water bath upto a temperature of 0-5 °C.

5. Then add -naphthol solution to it and cool it again upto 0- 5°C.

6. An orange red dye is formed.

REACTION:-

NH2

N NCl+

+optimum acidic

medium ,H + N N

OH

-naphtholbenzene-diazonium chloride


EXPERIMENT-19

Objective:- to prepare crystals of potash alum.K2SO4.Al2(SO4)3.24H2O

Theory:-

Potash alum is obtained when equimolar quantities of potassium sulphate and aluminium sulphate are mixed and the resulting solution is subjected to crystallization.

Aluminium because of its low density, high tensile strength and resistance to corrosion is widely used for the manufacture of airplanes, automobiles lawn furniture as well as for aluminium cans. Being good conductor of electricity it is used for transmission of electricity. Aluminium is also used for making utensils.

Alums are double sulphates having general formula

X2SO4. M2(SO4)3.24H2O

X = Monovalent cation; M = Trivalent cation

K2SO4.Al2(SO4)3.24H2O – Potash Alum

Na2SO4.Al2(SO4)3.24H2O - Soda Alum

Introduction

Potash alum is used in papermaking, in fire extinguishers, in food stuffs and in purification of water soda alum used in baking powders and chrome alum is used in tanning leather and water proofing fabrics.

Alum is also used as an astringent a substance or preparation that draws together or constricts body tissues and is effective in stopping the flow of blood or other secretions. Alum has also been used by conventional hairdressers for treating shaving cuts.

Apparatus and chemicals:-

Al2(SO4)3.18H2O

K2SO4

Porcelain dish, tripod stand.

Procedure:-

1. Weighed amount of Al2(SO4)3.18H2O is dissolved in water to make its near saturated solution 2. Similarly weighed amount of K2SO4 is dissolved in water to make its near saturated solution 3. The two solutions are mixed in a porcelain dish and then heated on wire gauze and concentrated the

solution to crystallization point. 4. The solution is then left overnight to crystallize 5. The mother liquor is decanted off and the crystals are dried with the help of filter paper


VOLUMETRIC ANALYSIS

EXPERIMENT-20

Aim: - to prepare 20

Msolution of ferrous ammonium sulphate [Mohr’s salt] and with the help of it find the

molarity and strength of the given KMnO4 solution

THEORY AND EQUATIONS:-

FeSO4.(NH4)2SO4.6H2O FeSO4 + (NH4)2SO4 + 6H2O

Only ferrous sulphate reacts with potassium permanganate

Oxidation of ferrous to ferric:-

[MnO4- + 8H+ + 5e- Mn+2 + 4H2O ] x 2

[ 2Fe+2 Fe2+3 + 2e- ] x 5

2MnO4- +16 H+ +10 Fe+2 2 Mn+2 + 8 H2O + 5 Fe2

+3

Or, 2KMnO4 + 8H2SO4 + 10 FeSO4 K2SO4 +2MnSO4 + 5Fe2(SO4)3 +8H2O

Indicator: - KMnO4 acts as self indicator.

Procedure:-

1. Prepared the 20

M Mohr salt solution

2. Filled the burette with permanganate solution

3. Pipetted out 25 ml of 20

M Mohr salt solution. Added 15-20 ml of H2SO4.

4. Then titration was started by slowly adding drop by drop potassium permanganate solution from burette

5. The pink coloured of the potassium permanganate solution disappeared on reaction with Mohr’s salt. 6. At one point the pink coloured of the potassium permanganate solution did not disappear. 7. This was the end point.

Observations:-

1) Molecular Weight of KMnO4 = 158 gm. 2) Molecular Weight of Mohr’s salt = 392 gm. 3) Weight of Mohr’s salt = 4.9 gm

4) Molarity of Mohr salt solution =20

M

Observation table for titration:-

S.NO. Initial reading of the burette(ml)

Final reading of the burette(ml)

Volume of KMnO4 solution used.

1

2 3


Calculations:-

4 4 Mohr

4 4

4

KMnO KMnO Mohr

KMnO 4 KMnO

By the Law of equivalence : -

meq. of Oxidising agent = meq. of Reducing agent

meq. of KMnO = meq. of Mohr's salt

Or, N x V (ml) = N x V (ml)

Or, M x n - factor for KMnO x V (mMohr Mohr

4 4 Mohr Mohr

4

KMnO KMnO

l) = M x n - factor for Mohr salt x V (ml)

[SINCE : - N = M x n - factor ]

n - factor for KMnO = 5

n - factor for Mohr = 1

Therefore : - M x 5 x V (ml) = M x 1 x V (ml

Mohr Mohr

4

4

KMnO

KMnO

)

M x 1 x V (ml) M =

5 x V (ml)

……………………………………………………………….

………………………………………………………………

…………………………………………………………….

44 KMnO 4Strength of KMnO solution = M x Molecular mass of KMnO

…………………………………..

Result:-

The molarity of given KMnO4 solution is = ………………………

The strength of given KMnO4 solution is = ………………………

Precautions

The Mohr salt solution should be carefully prepared

Sulphuric acid must be added before starting the titration

Error of parallax should be avoided while taking the burette reading


EXPERIMENT-21


Msolution of ferrous ammonium sulphate [Mohr’s salt] and with the help of it find the

molarity and strength of the given KMnO4 solution

EXPERIMENT-22


Msolution of oxalic acid and with the help of it find the molarity and strength of the given

KMnO4 solution

THEORY AND EQUATIONS:-

Oxidation of oxalate to carbon dioxide:-

[MnO4- + 8H+ + 5e- Mn+2 + 4H2O ] x 2

[ C2O4-2 2CO2 + 2e- ] x 5

2MnO4- +16 H+ +5 C2O4

-2 2 Mn+2 + 8 H2O + 10CO2

Or, 2KMnO4 + 3H2SO4 + 5 H2C2O4 K2SO4 +2MnSO4 +10CO2 +8H2O

Or, 2KMnO4 + 8H2SO4 + 10 FeSO4 K2SO4 +2MnSO4 + 5Fe2(SO4)3 +8H2O

Indicator: - KMnO4 acts as self indicator.

Procedure:-

1. Prepared the 20

M oxalic acid solution

2. Filled the burette with permanganate solution

3. Pipetted out 25 ml of 20

M oxalic acid solution. Added 15-20 ml of H2SO4.

4. heated the solution to about 60-70°C 5. Then titration was started by slowly adding drop by drop potassium permanganate solution from

burette 6. The pink coloured of the potassium permanganate solution disappeared on reaction with Mohr’s salt. 7. At one point the pink coloured of the potassium permanganate solution did not disappear. 8. This was the end point.

Observations:-

1. Molecular Weight of KMnO4 = 158 gm. 2. Molecular Weight of oxalic acid = 126 gm. 3. Weight of Mohr’s salt = 1.575 gm

4. Molarity of oxalic acid solution =20

M


Observation table for titration:-

S.NO. Initial reading of the

burette(ml)

Final reading of the

burette(ml)

Volume of KMnO4 solution

used.

1

2

3

Calculations:-

4 4

4

4

KMnO KMnO Oxalic Oxalic

KMnO 4 KMn

By the Law of equivalence : -

meq. of Oxidising agent = meq. of Reducing agent

meq. of KMnO = meq. of Oxalic acid

Or, N x V (ml) = N x V (ml)

Or, M x n - factor for KMnO x V4 Oxalic Oxalic

4 4

O

4

KMnO KMnO Oxalic

(ml) = M x n - factor for Oxalic acid x V (ml)

[SINCE : - N = M x n - factor ]

n - factor for KMnO = 5

n - factor for Mohr = 2

Therefore : - M x 5 x V (ml) = M x 2

Oxalic Oxalic

4

4

Oxalic

KMnO

KMnO

x V (ml)

M x 2 x V (ml) M =

5 x V (ml)

……………………………………………………………….

………………………………………………………………

…………………………………………………………….

44 KMnO 4Strength of KMnO solution = M x Molecular mass of KMnO

…………………………………..

Result:-

The molarity of given KMnO4 solution is = ………………………

The strength of given KMnO4 solution is = ………………………

Precautions

The Mohr salt solution should be carefully prepared.

Sulphuric acid must be added before starting the titration.

Error of parallax should be avoided while taking the burette reading.

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