Download doc - Practicals Xii

AMITY INTERNATIONAL SCHOOL-SAKET

CHEMISTRY PRACTICALS

CLASS-XII

EXPERIMENT No. 1

AIM (a) To prepare 100ml of M/20 solution of oxalic acid. (b)Using this calculate the molarity and strength of the given KMnO4 solution.

APPARATUS AND CHEMICALS REQUIRED- Oxalic acid, weighing bottle, weight box, volumetric flask, funnel, distilled water, chemical balance, beakers, conical flask, funnel, burette, pipette, clamp stand, tile, dilute H2SO4, KMnO4 solution.

THEORY- (a) Oxalic acid is a dicarboxylic acid having molar mass 126gmol-1. It is a primary standard and has the molecular formula COOH-COOH.2H2O. Its equivalent mass is 126/2 = 63 as its n factor is 2 as per the following reaction:

COOH-COOH 2CO2 + 2H+ + 2e-.

Calculation of amount of oxalic acid to be weighed to prepare 100ml M/20 solution:

wt. X 1000

M =

Mol. Wt V(ml)

PROCEDURE:

1. Weigh a clean dry bottle using a chemical balance.

2. Add more weights to the pan containing the weights for the weighing bottle.

3. Add oxalic acid in small amounts to the weighing bottle, so that the pans are balanced.

4. Remove the weighing bottle from the pan.

5. Using a funnel, transfer the oxalic acid to the volumetric flask.

6. Add a few drops of distilled water to dissolve the oxalic acid.

7. Make up the volume to the required level using distilled water.

8. The standard solution is prepared.

(b) THEORY-

1. The reaction between KMnO4 and oxalic acid is a redox reaction and the titration is therefore called a redox titration.

2. Oxalic acid is the reducing agent and KMnO4 is the oxidizing agent.

3. KMnO4 acts as an oxidizing agent in all the mediums; i.e. acidic, basic and neutral medium.

4. KMnO4 acts as the strongest oxidizing agent in the acidic medium and therefore dil. H2SO4 is added to the conical flask before starting the titration.

5. The titration between oxalic acid and KMnO4 is a slow reaction, therefore heat the oxalic acid solution to about 600C to increase the rate of the reaction.

IONIC EQUATIONS INVOLVED:

Reduction Half: MnO4- + 8H+ + 5e- Mn2+ + 4H2O] X 2

Oxidation Half: C2O42- 2CO2 + 2e- ] X 5

Overall Equation: 2MnO4- + 16H+ + 5C2O42- 2Mn2+ + 10CO2 + 8H2O

INDICATOR- KMnO4 acts as a self indicator.

END POINT- Colourless to light pink (KMnO4 in the burette)

PROCEDURE-

1. Fill the burette with KMnO4 solution.

2. Pipette out 10ml. of oxalic acid solution into the conical flask.

3. Add half a test tube of dil. H2SO4 and heat the solution to about 600C to increase the rate of the reaction.

4. Keep a glazed tile under the burette and place the conical flask on it.

5. Note down the initial reading of the burette.

6. Run down the KMnO4 solution into the conical flask drop wise with shaking.

7. Stop the titration when a permanent pink colour is obtained in the solution.

8. This is the end point. Note down the final burette reading.

9. Repeat the experiment until three concordant values are obtained.

OBSERVATION TABLE: (TO BE PUT UP ON THE BLANK SIDE USING A PENCIL)

Volume of Oxalic Acid solution taken =

S.No

BURETTE

READINGS

VOLUME OF KMnO4

INITIAL

FINAL

USED (ml)

1

2

3

4

5

Concordant Value =

CALCULATIONS: (TO BE PUT UP ON THE BLANK SIDE USING A PENCIL)

Using formula:

N1M1V1 = N2M2V2

Where N1=5 (for KMnO4), V1= , M1 =?

N2=2 (for oxalic acid), V2 = 10ml, M2 =

Strength = M X Molar Mass.

RESULT- (ON RULED SIDE)- The Molarity of KMnO4 =

And the strength of KMnO4 =

EXPERIMENT No. 2

AIM (a) To prepare 100ml of M/50 solution of Mohrs salt. (b) Using this calculate the molarity and strength of the given KMnO4 solution.

APPARATUS AND CHEMICALS REQUIRED- Mohrs salt, weighing bottle, weight box, volumetric flask, funnel, distilled water, chemical balance, dilute H2SO4, beakers, conical flask, funnel, burette, pipette, clamp stand, tile, KMnO4 solution.

THEORY- (a) Mohrs salt having the formula FeSO4.(NH4)2SO4.6H2O has molar mass 392gmol-1. It is a primary standard.

Its equivalent mass is 392/1 = 392 as its n factor is 1 as per the following reaction:

Fe2+ Fe3+ + e-

Calculation of amount of Mohrs Salt to be weighed to prepare 100ml M/20 solution:

wt. X 1000

M =

Mol. Wt V(ml)

PROCEDURE:

1. Weigh a clean dry bottle using a chemical balance.

2. Add more weights to the pan containing the weights for the weighing bottle.

3. Add Mohrs salt in small amounts to the weighing bottle, so that the pans are balanced.

4. Remove the weighing bottle from the pan.

5. Using a funnel, transfer the Mohrs salt to the volumetric flask.

6. Add about 5ml. of dilute H2SO4 to the flask followed by distilled water and dissolve the Mohrs salt.

7. Make up the volume to the required level using distilled water.

8. The standard solution is prepared.

(b) THEORY-

1. The reaction between KMnO4 and Mohrs salt is a redox reaction and the titration is therefore called a redox titration.

2. Mohrs salt is the reducing agent and KMnO4 is the oxidizing agent.

3. KMnO4 acts as an oxidizing agent in all the mediums; i.e. acidic, basic and neutral medium.

4. KMnO4 acts as the strongest oxidizing agent in the acidic medium and therefore dil. H2SO4 is added to the conical flask before starting the titration.

IONIC EQUATIONS INVOLVED:

Reduction Half: MnO4- + 8H+ + 5e- Mn2+ + 4H2O

Oxidation Half: 5Fe2+ 5Fe3+ + 5e-

Overall Equation: MnO4- + 8H+ + 5Fe2+ Mn2+ + 5Fe3+ + 4H2O

INDICATOR- KMnO4 acts as a self indicator.

END POINT- Colourless to light pink (KMnO4 in the burette)

PROCEDURE-

1. Fill the burette with KMnO4 solution.

2. Pipette out 10ml. of Mohrs salt solution into the conical flask.

3. Add half a test tube of dil. H2SO4.

4. Keep a glazed tile under the burette and place the conical flask on it.

5. Note down the initial reading of the burette.

6. Run down the KMnO4 solution into the conical flask drop wise with shaking.

7. Stop the titration when a permanent pink colour is obtained in the solution.

8. This is the end point. Note down the final burette reading.

9. Repeat the experiment until three concordant values are obtained.

OBSERVATION TABLE: (TO BE PUT UP ON THE BLANK SIDE USING A PENCIL)

Volume of Mohrs salt solution taken =

S.No

BURETTE

READINGS

VOLUME OF KMnO4

INITIAL

FINAL

USED (ml)

1

2

3

4

5

Concordant Value =

CALCULATIONS: (TO BE PUT UP ON THE BLANK SIDE USING A PENCIL)

Using formula:

N1M1V1 = N2M2V2

Where N1=5 (for KMnO4), V1= , M1 =?

N2 =1 (for Mohrs salt), V2 = 10ml, M2 =

Strength = M X Molar Mass.

RESULT- (ON RULED SIDE)- The Molarity of KMnO4 =

And the strength of KMnO4 =

EXPERIMENT No.3

AIM: To prepare a colloidal sol of starch.

THEORY: Starch forms a lyophilic sol with water which is the dispersion medium. The sol of starch can be prepared by water to about 1000C. The sol is quite stable and is not affected by the presence of an electrolytic impurity.

PROCEDURE:

EXPERIMENT

OBSERVATION

INFERENCE

Take 50 ml of distilled water in a

A colourless, transluscent sol is

Sol of starch has been prepared

beaker and heat it to about 1000C.

obtained

Add a thin paste of starch to water with stirring.

RESULT- Colloidal sol of starch has been prepared.

EXPERIMENT No.4

AIM: To prepare a colloidal sol of ferric hydroxide.

THEORY: Ferric hydroxide forms a lyophobic sol with water which is the dispersion medium. It is prepared by the hydrolysis of ferric chloride with boiling distilled water as per the reaction:

FeCl3 (aq) + 3H2O Fe(OH)3 + 3HCl (aq).

The HCl formed during the reaction tries to destabilize the sol and therefore should be removed from the sol by dialysis. A wine red sol of ferric hydroxide is obtained.

PROCEDURE:

EXPERIMENT

OBSERVATION

INFERENCE

Take 50 ml of distilled water in a

A wine red sol is obtained

Sol of ferric hydroxide has been prepared

beaker and heat it to about 1000C.

Add the solution of FeCl3 to water with stirring.

RESULT- Colloidal sol of ferric hydroxide has been prepared.

EXPERIMENT No.5

AIM: To prepare crystals of Mohrs salt.

THEORY: Mohrs salt i.e. ferrous ammonium sulphate [FeSO4.(NH4)2SO4.6H2O] is a double salt. It can be prepared by making equimolar solution of hydrated ferrous sulphate and ammonium sulphate in minimum amount of water. A few ml of dil. H2SO4 is added to prevent the hydrolysis of FeSO4.7H2O. Cooling of the hot saturated solution yields light green crystals of Mohrs salt.

FeSO4.7H2O + (NH4)2 SO4 FeSO4.(NH4)2SO4.6H2O + H2O

RESULT- Colour of the crystals: Light green

Shape of the crystals: Monoclinic.

NOTE DRY THE CRYSTALS, PUT THEM IN A ZIP POUCH AND PASTE THEM IN YOUR FILES ON THE BLANK PAGE.

EXPERIMENT No.6

AIM: To prepare crystals of Potash alum.

THEORY: Potash alum, a double salt, commonly known as fitkari has the formula K2SO4.Al2(SO4)3.24H2O. It can be prepared by making equimolar solution of potassium sulphate and aluminium sulphate in minimum amount of water. A few ml of dil. H2SO4 is added to prevent the hydrolysis of Al2(SO4)3.18H2O. Cooling of the hot saturated solution yields colourless crystals of Potash alum.

K2SO4 + Al2(SO4)3.18H2O + 6H2O K2SO4.Al2(SO4)3.24H2O

RESULT- Colour of the crystals: Colourless

Shape of the crystals: Octahedral.

NOTE DRY THE CRYSTALS, PUT THEM IN A ZIP POUCH AND PASTE THEM IN YOUR FILES ON THE BLANK PAGE.

EXPERIMENT No.7

AIM: To separate the coloured components present in a mixture of red and blue ink by ascending paper chromatography and find their Rf values.

THEORY: In this type of chromatography a special adsorbent paper (Whatman filter paper) is used. Moisture adsorbed on this Whatman filter paper acts as stationary phase and the solvent acts as the mobile phase. The mixture to be separated is spotted at one end of the paper. This paper is then developed in a particular solvent by placing the paper in a gas jar, taking care that the spot is above the solvent. The solvent rises due to capillary action and the components get separated out as they rise up with the solvent at different rates. The developed paper is called a chromatogram.

Rf (retention factor) values are then calculated, which is the ratio of the distance moved by the component to the distance moved by the solvent front.

Rf = Distance traveled by the component

Distance traveled by the solvent front

OBSERVATIONS AND CALCULATIONS: (ON THE BLANK PAGE, USING A PENCIL)

S.No

SUBSTANCE

DISTANCE TRAVELLED BY

DISTANCE TRAVELLED BY

Rf VALUE

DIFFERENT COMPONENTS

SOLVENT

1

RED + BLUE INK

2

RED + BLUE INK

RESULT: (ON RULED SIDE) - Rf of blue ink =

Rf of red ink =

NOTE: PASTE THE CHROMATOGRAM ON THE BLANK SIDE AND MARK THE DISTANCE TRAVELLED BY THE INDIVIDUAL COMPONENTS AND THE SOLVENT FRONT USING A PENCIL.

EXPERIMENT No.8

AIM: To test the presence of unsaturation in the given organic compound.

PROCEDURE:

S.No

EXPERIMENT

OBSERVATION

INFERENCE

1

BAEYER'S TEST OR alk.KMnO4 TEST

Dissolve organic compound in water/acetone and add a few drop of Baeyer's reagent and shake

Pink colour of KMnO4 decolorizes.

Unsaturation present in the organic compound.

EQUATIONS: (ON BLANK SIDE USING A PENCIL)

2KMnO4 + H2O 2KOH + 2MnO2 + 3[O]

>C =C< + H2O + [O] >C(OH) (OH)C< + KOH

RESULT: (ON RULED SIDE) Unsaturation is present in the given organic compound.

EXPERIMENT No.9

AIM: To test the presence of alcoholic group in the given organic compound.

PROCEDURE:

S.No

EXPERIMENT

OBSERVATION

INFERENCE

1

CERRIC AMMONIUM NITRATE TEST

Organic compound + few drops of cerric ammonium nitrate solution. Shake well.

A pink or red colour appears.

Alcoholic OH group present.

2

ESTER TEST

Organic compound + few drops of glacial acetic acid + 1-2 drops of conc. H2SO4 + warm on water bath for 5 min. Cool and pour into 15ml of Na2CO3 solution. Smell the contents.

A fruity smell is obtained

Alcoholic OH group present


1. ROH + (NH4)2Ce(NO3)6 (NH4)2[Ce(OR)(NO3)5] + HNO3

Cerric amm. nitrate pink or red

2. ROH + CH3COOH CH3COOR + H2O

RESULT: (ON RULED SIDE) - Alcoholic OH present in the given organic compound.

EXPERIMENT No.10

AIM: To test the presence of phenolic group in the given organic compound.

PROCEDURE:

S.No

EXPERIMENT

OBSERVATION

INFERENCE

1

LITMUS TEST

Organic compound + few drops of blue litmus solution.

Blue litmus turns red.

Phenolic OH group present.

2

NEUTRAL FeCl3 TEST

Organic compound + few drops of neutral FeCl3 solution.

A violet colouration is obtained.


3

LIEBERMANN NITROSO TEST

Organic compound + sodium nitrite + conc. H2SO4

A deep blue or green colouration is obtained which turns red on the addition of water. The blue or green colour reappears on the addition of NaOH.



1. HO

(PHENOL)

+ FeCl3

2. Phenol (structure) NaNO2 + H2SO4 HO N=O

O = - NOH conc. H2SO4 / PHENOL(structure)

[HO N= = OH+] HSO4- H2O

(Deep Blue)

[HO N= = O] NaOH Sodium salt of phenol indophenol

Phenol indophenol (red) (blue)

RESULT: (ON RULED SIDE) Phenolic OH present in the given organic compound.

{ equations are incomplete}

EXPERIMENT No.11

AIM: To test the presence of aldehydic group in the given organic compound.

PROCEDURE:

S.No

EXPERIMENT

OBSERVATION

INFERENCE

1

2,4-DNP TEST

Organic compound + 2,4-DNP

Crystalline orange ppt. obtained

Carbonyl group present.

2

TOLLENS TEST

Organic compound + Tollens reagent (amm. silver nitrate solution). Heat on water bath.

A silver mirror is obtained the walls of the test tube.

Aldehydic group present.

3

BENEDICTS / FEHLINGS TEST

Organic compound + Benedicts reagent/ Fehlings reagent (A mixture of equal amounts of Fehlings A and Fehlings B). Heat.

A brick red ppt. is obtained.


4

SCHIFFS TEST

Organic compound + Schiffs reagent

A red/ pink/violet colouration is obtained.



1. RCHO + NH2NH =

(equation 1 is incomplete)

2. RCHO + 2[Ag(NH3)2]+ + 3OH- RCOO- + 4NH3 + 2Ag + 2H2O

3. RCHO + 2Cu2+ + 5OH- RCOO- + Cu2O + 3H2O

RESULT: (ON RULED SIDE ) Aldehyde present in the given organic compound.

EXPERIMENT No.12

AIM: To test the presence of ketonic group in the given organic compound.

PROCEDURE:

S.No

EXPERIMENT

OBSERVATION

INFERENCE

1

2,4-DNP TEST

Organic compound + 2,4-DNP

Crystalline orange ppt. obtained

Carbonyl group present.

2

m-DINITROBENZENE TEST

Organic compound + m- dinitrobenzene + NaOH


Ketonic group present.

3

SODIUM NITROPRUSSIDE TEST

Organic compound + sodium nitroprusside + NaOH

A red colouration is obtained.

Ketonic group present.


1. CH3COCH3 + OH- CH3COCH2- + H2O

[Fe(CN)5NO]2 - + CH3COCH2- [Fe(CN)5NO(CH2COCH3)]3 -

Nitroprusside ion Red complex

RESULT: : (ON RULED SIDE ) Ketone present in the given organic compound.

EXPERIMENT No.13

AIM: To test the presence of carboxylic acid group in the given organic compound.

PROCEDURE:

S.No

EXPERIMENT

OBSERVATION

INFERENCE

1

LITMUS TEST

Organic compound + blue litmus

Blue litmus turns red

Carboxylic acid may be present.

2

SODIUM BICARBONATE TEST

Organic compound + aq. NaHCO3

Brisk effervescence is obtained.

Carboxylic acid group present.

3

ESTER TEST

Organic compound + few drops of alcohol + 2-3 drops of conc. H2SO4 + heat on a water bath. Cool the contents and pour them into cold water.

A fruity smell is obtained.

Carboxylic acid group present.


1. RCOOH + NaHCO3 RCOONa + H2O + CO2

2. RCOOH + CH3CH2OH conc. H2SO4 RCOO CH2CH3

RESULT: : (ON RULED SIDE ) Carboxylic acid present in the given organic compound.

EXPERIMENT No.14

AIM: To test the presence of amino group in the given organic compound.

PROCEDURE:

S.No

EXPERIMENT

OBSERVATION

INFERENCE

1

LITMUS TEST

Organic compound + few drops of red litmus solution.

Red litmus turns blue

Amino group present.

2

SOLUBILITY TEST

Organic compound + 1-2 ml of dil.HCl. Shake well.

Organic compound dissolves.

Amino group present

3

CARBYLAMINE TEST

Organic compound + CHCl3 + Alc.KOH. Heat

An obnoxious smell is obtained.

Primary amine present.

4

AZO DYE TEST

Dissolve organic compound in dil.HCl and cool in ice. Add ice cold NaNO2 solution to it. Mix well. Add ice cold solution of - naphthol + NaOH.

A red or orange dye is obtained.

Primary aromatic amino group present.


1. R-NH2 + HCl R- NH3+Cl-

amine amine salt

2. R-NH2 + CHCl3 + 3KOH R- N C + 3KCl + 3H2O

Isocyanide

or carbylamine

3. NaNO2 + HCl HNO2 + NaCl

ArNH2 + HNO2 + HCl Ar- N+ N-Cl + 2H2O

Aromatic Aryldiazonium chloride

10amine (stable between 0- 50C)

- naphthol (draw structure) + Ar- N+ N-Cl (draw structure of the azo dye obtained) + NaCl + H2O

RESULT: : (ON RULED SIDE ) Amino present in the given organic compound.

NOTE: After performing the carbylamine test add 1ml conc.HCl to the reaction mixture and heat to decompose the isocyanide formed and throw the reaction mixture into running water.

EXPERIMENT No.15

AIM: To test the presence of carbohydrate in the given food sample.

PROCEDURE:

S.No

EXPERIMENT

OBSERVATION

INFERENCE

1

CONC H2SO4 TEST

Food sample + conc. H2SO4. Heat

Charring occurs with smell of burnt sugar

Carbohydrate present.

2

MOLISCHS TEST

Food sample + Molischs reagent (1% alcoholic solution of naphthol) + conc. H2SO4 along the sides of the test tube.

A purple ring is obtained at the junction of the two layers.

Carbohydrate present.

3

BENEDICTS / FEHLINGS TEST

Food sample + Benedicts reagent/ Fehlings reagent (A mixture of equal amounts of Fehlings A and Fehlings B). Heat.

A red ppt. is obtained.

Carbohydrate

present.

4

TOLLENS TEST

Food sample + Tollens reagent (amm. silver nitrate solution). Heat on water bath.

A silver mirror is obtained the walls of the test tube.

Carbohydrate

present.


1. CHO(CHOH)4CH2OH + 2Cu2+ + 5OH- COOH(CHOH)4CH2OH + Cu2O + 3H2O

Glucose Gluconic acid

2. CHO(CHOH)4CH2OH + 2[Ag(NH3)2]+ + 3OH- COOH(CHOH)4CH2OH + 4NH3

Glucose (Gluconic acid) + 2Ag + 2H2O

RESULT: : (ON RULED SIDE ) The food sample has been tested for carbohydrate.

EXPERIMENT No.16

AIM: To test the presence of oil or fat in the given food sample.

PROCEDURE:

S.No

EXPERIMENT

OBSERVATION

INFERENCE

1

SOLUBILITY TEST

Food sample + water

Food sample + chloroform(CHCl3)

Does not dissolve

Miscible

Oil / fat present.

2

SPOT TEST

Smear the food sample on paper.

A translucent spot is observed.

Oil / fat present.

3

ACROLEIN TEST

Food sample + KHSO4. Heat

An irritating odour is obtained.

Oil / fat present.


Oil/ fat heat glycerol + fatty acid

CH2 (OH)CH(OH) CH2 (OH) KHSO4, Heat CH2CHCHO (acrolein) + 2H2O

RESULT: (ON RULED SIDE ) The food sample has been tested for oil/fat

NOTE THE PARER OBTAINED IN SPOT TEST TO BE PUT IN A ZIP POUCH AND PASTED ON THE BLANK SIDE.

EXPERIMENT No.17

AIM: To test the presence of protein in the given food sample.

PROCEDURE:

S.No

f

OBSERVATION

INFERENCE

1

BIURET TEST

Food sample + few drops of NaOH + CuSO4 solution.


Protein present.

2

XANTHOPROTEIC TEST

Food sample + few drops of conc. HNO3. Heat.

A yellow ppt. is obtained.

Protein present.

3

NINHYDRIN TEST

Food sample + few drops of 0.15 ninhydrin solution. Boil the contents.

A blue colour is obtained.

Protein present.

RESULT: (ON RULED SIDE ) The food sample has been tested for proteins.

How do we determine the strength of a given acid or base?

Determination of the strength is based on the Law of Equivalents. According to this law, the number of equivalence of the substance to be titrated is equal to the number of equivalence of the titrant used.

Consider an acid-alkali titration. V1 cm3 is that of an acid solution of normality N1 required to neutralize V2 cm3 of a base of normality N2.

We know that 1000 cm3 of 1N acid solution contains acid = 1 gram equivalent

V1 cm3of 1N acid solution contains acid= V1/1000 gram equivalents

Thus number of gram equivalents of acid in V1 cm3 of N1 acid solution is;

Similarly, number of gram equivalents of base in V2 cm3 of N2 basic solution is;

By the law of equivalents, at the end point,

i.e,

This is called the Normality Equation.

Similarly, Molarity equation can be written as,

Here we determine the strength of HCl by titrating it against a standard solution of sodium carbonate and they react to form NaCl, CO2 and water. The chemical reaction can be represented as;

Here 2 moles of sodium carbonate reacts with 1 mole of HCl. So according to Molarity equation,