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) THEORY1. 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. 6. 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) PROCEDURE1. 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 = BURETT S.No
E INITIAL
1 2 3 4 5
READINGS FINAL
VOLUME OF KMnO4 USED (ml)
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 Mohr’s salt. (b) Using this calculate the molarity and strength of the given KMnO4 solution. APPARATUS AND CHEMICALS REQUIRED- Mohr’s 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) Mohr’s 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+ + eCalculation of amount of Mohr’s 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 Mohr’s 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 Mohr’s salt to the volumetric flask. 6. Add about 5ml. of dilute H2SO4 to the flask followed by distilled water and dissolve the Mohr’s salt. 7. Make up the volume to the required level using distilled water. 8. The standard solution is prepared.
(b) THEORY1. The reaction between KMnO4 and Mohr’s salt is a redox reaction and the titration is therefore called a redox titration. 2. Mohr’s 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. 5. IONIC EQUATIONS INVOLVED: Reduction Half: MnO4- + 8H+ + 5e- → Mn2+ + 4H2O Oxidation Half: 5Fe2+ → 5Fe3+ + 5eOverall Equation: MnO4- + 8H+ + 5Fe2+ → Mn2+ + 5Fe3+ + 4H2O INDICATOR- KMnO4 acts as a self indicator. END POINT- Colourless to light pink (KMnO4 in the burette) PROCEDURE1. Fill the burette with KMnO4 solution. 2. Pipette out 10ml. of Mohr’s 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. 10. OBSERVATION TABLE: (TO BE PUT UP ON THE BLANK SIDE USING A PENCIL) Volume of Mohr’s salt solution taken = BURETT S.No
E INITIAL
1 2 3 4 5
READINGS FINAL
VOLUME OF KMnO4 USED (ml)
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 Mohr’s 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 Take 50 ml of distilled water in a beaker and heat it to about 1000C. Add a thin paste of starch to water with stirring.
OBSERVATION A colourless, transluscent sol is obtained
INFERENCE Sol of starch has been prepared
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 Take 50 ml of distilled water in a beaker and heat it to about 1000C. Add the solution of FeCl3 to water with stirring.
OBSERVATION A wine red sol is obtained
RESULT- Colloidal sol of ferric hydroxide has been prepared.
INFERENCE Sol of ferric hydroxide has been prepared
EXPERIMENT No.5 AIM: To prepare crystals of Mohr’s salt. THEORY: Mohr’s 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 Mohr’s 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
1 2
RED + BLUE INK RED + BLUE INK
DISTANCE TRAVELLED BY DIFFERENT COMPONENTS
DISTANCE TRAVELLED BY SOLVENT
Rf VALUE
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 1
EXPERIMENT BAEYER'S TEST OR alk.KMnO4 TEST Dissolve organic compound in water/acetone and add a few drop of Baeyer's reagent and shake
OBSERVATION
INFERENCE
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 1
2
EXPERIMENT CERRIC AMMONIUM NITRATE TEST Organic compound + few drops of cerric ammonium nitrate solution. Shake well.
OBSERVATION
INFERENCE
A pink or red colour appears.
Alcoholic –OH group present.
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
EQUATIONS: (ON BLANK SIDE USING A PENCIL) 1. ROH + (NH4)2Ce(NO3)6 → (NH4)2[Ce(OR)(NO3)5] Cerric amm. nitrate pink or red 2. ROH + CH3COOH → CH3COOR + H2O
+
HNO3
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 1 2
3
EXPERIMENT LITMUS TEST Organic compound + few drops of blue litmus solution. NEUTRAL FeCl3 TEST Organic compound + few drops of neutral FeCl3 solution.
LIEBERMANN NITROSO TEST Organic compound + sodium nitrite + conc. H2SO4
EQUATIONS: (ON 1. HO —
OBSERVATION Blue litmus turns red.
INFERENCE Phenolic –OH group present.
A violet colouration is obtained.
Phenolic –OH group present.
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.
Phenolic –OH group present.
BLANK SIDE USING A PENCIL) (PHENOL) + FeCl3 →
2.
Phenol (structure)
↔O=
[HO (Deep Blue)
NaNO2 + H2SO4
- NOH
–N=
HO
conc. H2SO4 / PHENOL(structure)
= OH+] HSO4-
H2O
–N=O
[HO
–N=
= O] NaOH
Phenol indophenol (red)
Sodium salt of phenol indophenol (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 1 2
3
4
EXPERIMENT 2,4-DNP TEST Organic compound + 2,4-DNP TOLLEN’S TEST Organic compound + Tollen’s reagent (amm. silver nitrate solution). Heat on water bath. BENEDICT’S / FEHLING’S TEST Organic compound + Benedict’s reagent/ Fehling’s reagent (A mixture of equal amounts of Fehling’s A and Fehling’s B). Heat. SCHIFF”S TEST Organic compound + Schiff’s reagent
OBSERVATION
INFERENCE
Crystalline orange ppt. obtained
Carbonyl group present.
A silver mirror is obtained the walls of the test tube.
Aldehydic group present.
A brick red ppt. is obtained.
Aldehydic group present.
A red/ pink/violet colouration is obtained.
Aldehydic group present.
EQUATIONS: (ON BLANK SIDE USING A PENCIL) 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 1 2 3
EXPERIMENT 2,4-DNP TEST Organic compound + 2,4-DNP m-DINITROBENZENE TEST Organic compound + mdinitrobenzene + NaOH SODIUM NITROPRUSSIDE TEST Organic compound + sodium nitroprusside + NaOH
OBSERVATION
INFERENCE
Crystalline orange ppt. obtained
Carbonyl group present.
A violet colouration is obtained.
Ketonic group present.
A red colouration is obtained.
Ketonic group present.
EQUATIONS: (ON BLANK SIDE USING A PENCIL) 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 1 2 3
EXPERIMENT LITMUS TEST Organic compound + blue litmus SODIUM BICARBONATE TEST Organic compound + aq. NaHCO3 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.
OBSERVATION
INFERENCE
Blue litmus turns red
Carboxylic acid may be present.
Brisk effervescence is obtained.
Carboxylic acid group present.
A fruity smell is obtained.
Carboxylic acid group present.
EQUATIONS: (ON BLANK SIDE USING A PENCIL) 1. RCOOH + NaHCO3 → RCOONa + H2O + CO2↑ 2. RCOOH + CH3CH2OH
conc. H SO 2 4
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 1 2 3 4
EXPERIMENT LITMUS TEST Organic compound + few drops of red litmus solution.
OBSERVATION Red litmus turns blue
SOLUBILITY TEST Organic compound + 1-2 ml of Organic compound dil.HCl. Shake well. dissolves. CARBYLAMINE TEST Organic compound + CHCl3 + An obnoxious smell Alc.KOH. Heat is obtained. AZO DYE TEST Dissolve organic compound in A red or orange dye dil.HCl and cool in ice. Add ice is obtained. cold NaNO2 solution to it. Mix well. Add ice cold solution of β- naphthol + NaOH.
INFERENCE Amino group present. Amino group present Primary amine present. Primary aromatic amino group present.
EQUATIONS: (ON BLANK SIDE USING A PENCIL) 1. R-NH2 + HCl → R- NH3+Clamine 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 0 1 amine (stable between 0- 50C) β- 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 1 2
3
4
EXPERIMENT CONC H2SO4 TEST Food sample + conc. H2SO4. Heat
OBSERVATION Charring occurs with smell of burnt sugar
MOLISCH’S TEST Food sample + Molisch’s reagent (1% A purple ring is alcoholic solution of α naphthol) + obtained at the conc. H2SO4 along the sides of the junction of the two test tube. layers. BENEDICT’S / FEHLING’S TEST Food sample + Benedict’s reagent/ A red ppt. is Fehling’s reagent (A mixture of obtained. equal amounts of Fehling’s A and Fehling’s B). Heat. TOLLEN’S TEST Food sample + Tollen’s reagent A silver mirror is (amm. silver nitrate solution). Heat obtained the walls on water bath. of the test tube.
INFERENCE Carbohydrate present. Carbohydrate present.
Carbohydrate present.
Carbohydrate present.
EQUATIONS: (ON BLANK SIDE USING A PENCIL) 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 1
EXPERIMENT
OBSERVATION
SOLUBILITY TEST Food sample + water Food sample + chloroform(CHCl3)
2
INFERENCE
Does not dissolve Miscible
Oil / fat present.
A translucent spot is observed.
Oil / fat present.
An irritating odour is obtained.
Oil / fat present.
SPOT TEST Smear the food sample on paper.
3
ACROLEIN TEST Heat
Food sample + KHSO4.
EQUATIONS: (ON BLANK SIDE USING A PENCIL) Oil/ fat
heat
CH2 (OH)CH(OH) CH2 (OH)
glycerol + fatty acid KHSO4, Heat
CH2═CHCHO (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 1
2
f BIURET TEST Food sample + few drops of NaOH + CuSO4 solution.
INFERENCE
A violet colouration is obtained.
Protein present.
A yellow ppt. is obtained.
Protein present.
A blue colour is obtained.
Protein present.
XANTHOPROTEIC TEST Food sample + few drops of conc. HNO3. Heat.
3
OBSERVATION
NINHYDRIN TEST Food sample + few drops of 0.15 ninhydrin solution. Boil the contents.
RESULT: (ON RULED SIDE ) The food sample has been tested for proteins.
