Chemlab Practicals (Experiment 1-4)

detection of carbon
-heated dry egg albumin

=char/charring (presence of carbon)
=moisture (presence of hydrogen)

Detection of Nitrogen
-heated urea + soda lime

=ammonia (NH₃)
(urea + CaHNaO₂——> NH₃)

Detection of Sulfur
-dry egg albumin + lead acetate + dil. sodium hydroxide

=lead sulfide (PbS)
=black precipitate/solution
(Pb(Ch₃COO)₂ + Na₂S —NaOH—> PbS + 2Ch₃COONa)

Detection of Phosphorus
dry egg albumin + ammonium molybdate + conc. nitric acid

=ammonium phospho-molybdate (3NH₄PO4 12MoO₃)
=yellow solution)/precipitate
(3NH₄⁼ +12MoO₄⁺ + PO­₄^3- + 24H^{+  —→}  3NH₄PO4 12MoO₃ + 12H₂O)

Detection of Halogens (Beilstein Test)
-heated Cu wire

=green flame

Sublimation
-Benzoic acid + Sodium Chloride

=crystals (at the bottom of the Erlenmeyer Flask)
(C₆H₅COOH + NaCl₂ —> pure crystals)

Recrystallization
-impure acetanilide + congo red + animal charcoal

=crystals
(bigger crystals are more pure)

(C₆H₅NHCOCH₃ + congo red + animal charcoal —> pure crystals)

Distillation
-Ethanol (C₂H­₅OH) + red dye

=pure ethanol (C₂H­₅OH) (distillate)

Baeyer’s Test for Unsaturation (alkane: Hexane)
-Potassium Permanganate + Hexane

=Purple Solution (No Reaction)
(C₆H₁₄ + KMnO₄—> NR)

2H

Bromine Water Test (Alkane: Hexane)
-Bromine Solution + Hexane —-UV light—→

=Bromohexane (C6H13Br)
=Very pale-clear solution
(Br₂ + C₆H₁₄ = C₆H₁₃Br + HBr)

3H

Iodine Test (Alkane: Hexane)
-Alc. Iodine + Hexane

=unmixed reddish-yellow solution (No reaction)

Ignition Test (combustion)
-Hexane + Oxygen

= Carbone Dioxide and Water
=orange luminous flame
(2C₆H₁₄ + 19O₂ —> 12CO₂ + 14H₂0)

Baeyer’s Test for Unsaturation (alkyne: Acetylene)
-Potassium Permanganate + Acetylene

=Manganese Dioxide (MnO₂)
=Brown Precipitate
(2C₂H₂ + 10KMno₄ + 2H₂O —→ 10MnO₂ + 10KOH + 6 Co₂)

2

Bromine Water Test (Alkyne: Acetylene)
-Bromine Solution + Acetylene —-UV light—→

=1,2-Dibromoethylene (C₂H₂Br₂₎
=very pale yellow solution
(Br₂ + C₂H₂ ——> C₂H₂Br₂₎

Iodine Test (Alkyne: Acetylene)
-Alcoholic Iodine+ Acetylene —-UV light—→

=1,2-Diiodoethylene (C₂H₂I₂₎
=orange-yellow solution
(I₂ + C₂H₂ ——> C₂H₂I₂₎

Formation of Cuprous Acetylide

- Copper Chloride + Ammoniacal Solution + Acetylene

=Cuprous Acetylide (Cu₂C₂)
= chocolate brown precipitate)
(CuCl₂ + 2NH₄OH + C₂H₂ —→  Cu₂C₂ + 2NH₄Cl + 2H₂O)

Preparation of Anhydrous Alcohol
-95% Ethanol + calcium carbide

=100% Anhydrous Ethanol
(C₂H­₅OH + CaC₂ à C₂H­₅OH + Ca(OH)₂ + C₂H₂)

Test for Water in Alcohols
ETHYL ALCOHOL
-Copper Sulfate + Ethanol

= Blue Copper Sulfate
(CuSO₄ + C₂H₅OH —>Blue CuSO­₄)

ANHYDROUS ETHYL ALCOHOL
-Copper Sulfate + Anhydrous Ethanol

= White Copper Sulfate
(CuSO₄ + C₂H₅OH —>White CuSO­₄)

CLEAR SOLUTION (ESTERS)

Esterification

ETHYL ALCOHOL
-Ethanol + Acetic Acid + Conc. Sulfuric acid

= Ethyl Acetate (rubbery odor)
(C₂H₅OH + CH₃COOH –Conc. H₂SO₄—> CH₃COOC₂H₅  + H₂O)
(fully oxidized)

METHYL ALCOHOL
-Methanol + Salicylic Acid + Conc. Sulfuric acid

= Methyl Salicylate (minty odor)
(CH₃OH + C₆H₄OHCOOH –Conc. H₂SO₄—> C₆H₄OHCOOCH₃ + H₂O)

Oxidation

ETHYL ALCOHOL
-Ethanol + Potassium Dichromate + Conc. Sulfuric acid

= Acetic Acid (Green)
(C₂H₅OH + K₂Cr₂O₇ + Conc. H₂SO₄ —> CH₃COOH)

ISOPROPYL ALCOHOL
-Isopropanol + Potassium Dichromate + Conc. Sulfuric acid

= Acetone (Green)
(CH(CH₃)₂OH + K₂Cr₂O₇ + Conc. H₂SO₄ —> CH₃COCH₃₎

TERT BUTYL ALCOHOL
-Tert-butyl Alcohol+ Potassium Dichromate + Conc. Sulfuric acid

= No reaction (orange)

Replacement of the Hydroxyl Group with Halogen: Lucas Test

ETHYL ALCOHOL
-Ethanol + Hydrochloric Acid + Zinc Chloride

= No reaction
(C₂H₅OH + HCl —ZnCl₂—> C₂H₅Cl+ HOH)

ISOPROPYL ALCOHOL
-Isopropanol + Hydrochloric Acid + Zinc Chloride

= No Reaction
(CH(CH₃)₂OH + HCl —-ZnCl₂—→ CH(CH₃)₂Cl + HOH)

TERT BUTYL ALCOHOL
-Tert-butyl Alcohol+ + Hydrochloric Acid + Zinc Chloride

= cloudiness/ turbidity
(C(CH₃)₃OH + HCl —-ZnCl₂—→ C(CH₃)₃Cl + HOH)