Chemistry Practical Experiments Class 12 – Complete Lab Manual CBSE

List of Experiments (CBSE Class 12)

Category	Experiments	Marks
Volumetric Analysis	Acid-base, Iodometric titrations	8
Salt Analysis	Cation & Anion identification	8
Content-based	Preparation, Tests	6
Project + Viva	Investigatory project	8

Volumetric Analysis

Experiment 1: Oxalic Acid vs KMnO4 Titration

Aim

To determine the strength of a given solution of oxalic acid by titrating it against standard KMnO4 solution.

Apparatus

Burette, pipette (20 ml), conical flask, burette stand, white tile.

Chemicals

Oxalic acid solution (given), standard KMnO4, dilute H2SO4.

Theory

Procedure

1. Rinse the burette with KMnO4 and fill it
2. Pipette out 20 ml of oxalic acid in a conical flask
3. Add 10 ml of dilute H2SO4
4. Heat the solution to 60-70°C
5. Titrate with KMnO4 until permanent light pink color appears
6. Repeat for concordant readings

Observation Table

S.No	Initial Reading	Final Reading	Volume of KMnO4
1	0.0 ml	15.5 ml	15.5 ml
2	0.0 ml	15.4 ml	15.4 ml
3	0.0 ml	15.5 ml	15.5 ml

Concordant volume = 15.5 ml

Precautions

1. Heat oxalic acid before titration
2. Do not use indicator – KMnO4 is self-indicator
3. Add KMnO4 slowly dropwise
4. Titrate while solution is hot

Experiment 2: Mohr Salt vs KMnO4

Aim

To determine the percentage of iron in Mohr salt using KMnO4.

Reaction

Salt Analysis

Cation Analysis – Group Tests

Group	Reagent	Cations	Observation
I	Dil. HCl	Pb2+	White ppt
II	H2S + dil HCl	Cu2+, Pb2+	Black ppt (Cu), Yellow ppt (As)
III	NH4Cl + NH4OH	Fe3+, Al3+	Reddish brown (Fe), White (Al)
IV	H2S + NH4OH	Zn2+, Mn2+, Co2+, Ni2+	White (Zn), Flesh colored (Mn)
V	(NH4)2CO3	Ba2+, Ca2+, Sr2+	White ppt
VI	No group reagent	Mg2+, Na+, K+, NH4+	Identified by specific tests

Anion Analysis

Anion	Test	Observation
CO3²⁻	Dil. HCl	Effervescence, gas turns lime water milky
SO4²⁻	BaCl2 solution	White ppt insoluble in conc. HCl
Cl⁻	AgNO3	White ppt soluble in NH4OH
NO3⁻	Ring test (FeSO4 + conc. H2SO4)	Brown ring at junction
S²⁻	Lead acetate paper	Black stain
CH3COO⁻	Heat with H2SO4	Vinegar-like smell

Sample Salt Analysis

Salt Given: FeSO4.7H2O (Ferrous Sulphate)

Physical Examination

• Color: Bluish green
• Smell: Odorless
• Solubility: Soluble in water

Dry Tests

• Heating: Loses water, turns white then brown
• Flame test: No characteristic color

Wet Tests for Cation (Fe²⁺)

• NaOH: Dirty green precipitate turning brown
• NH4OH: Dirty green ppt
• K4[Fe(CN)6]: Blue precipitate (Turnbulls blue)

Wet Tests for Anion (SO4²⁻)

• BaCl2: White precipitate insoluble in conc. HCl
• Lead acetate: White precipitate

Content-Based Experiments

Experiment: Tests for Carbohydrates

Test	Reagent	Glucose	Sucrose	Starch
Molischs	α-naphthol + H2SO4	Violet ring	Violet ring	Violet ring
Fehlings	Fehlings A + B	Red ppt	No reaction	No reaction
Benedicts	Benedicts reagent	Red/green ppt	No reaction	No reaction
Tollens	Ammoniacal AgNO3	Silver mirror	No reaction	No reaction
Iodine	I2 solution	No change	No change	Blue color

Experiment: Tests for Proteins

• Biuret Test: Violet color with NaOH + CuSO4
• Xanthoproteic: Yellow color with conc. HNO3
• Ninhydrin: Purple color

Experiment: Tests for Fats and Oils

• Translucent spot test: Permanent oily spot on paper
• Acrolein test: Pungent smell with KHSO4

Practical Exam Tips

1. Practice titrations multiple times
2. Memorize confirmatory tests for all ions
3. Write observations clearly in table format
4. Show all calculations step by step
5. Prepare viva questions in advance
6. Maintain clean apparatus

Common Viva Questions

1. Why is H2SO4 added in permanganometry?
2. What is the role of KMnO4 as self-indicator?
3. Why is the solution heated before titration?
4. Differentiate between true solution and colloidal solution
5. What is the principle of paper chromatography?

Important Class 12 Chemistry Practicals: Detailed Procedures

Practical 1: Salt Analysis (Qualitative Analysis)

Salt analysis involves identifying the cation and anion in an unknown inorganic salt. This is one of the most important practicals in Class 12 Chemistry.

Preliminary Tests:

• Colour: Cu2+ = blue/green; Fe3+ = yellow/brown; Fe2+ = light green; Mn2+ = light pink; Co2+ = pink; Ni2+ = green
• Smell: Ammonical (NH4+ ions), rotten egg (S2- ions), vinegar (CH3COO- ions)
• Solubility: Test in water, dilute HCl, and dilute H2SO4

Confirmatory Tests for Common Anions:

• CO3 2-: Add dilute H2SO4 — CO2 gas turns lime water milky
• SO4 2-: Add BaCl2 solution — white precipitate (BaSO4) insoluble in HCl
• Cl-: Add AgNO3 solution — white curdy precipitate (AgCl) soluble in NH4OH
• NO3-: Brown ring test — FeSO4 + conc. H2SO4 — brown ring at the interface

Practical 2: Preparation of an Organic Compound — Aspirin (Acetylsalicylic Acid)

• Principle: Salicylic acid reacts with acetic anhydride in the presence of phosphoric acid to form aspirin
• Procedure: Take 2g salicylic acid in a flask. Add 3mL acetic anhydride and 5 drops phosphoric acid. Heat on a water bath for 15 minutes. Pour into cold water. Filter and recrystallise.
• Characterisation: Melting point of pure aspirin = 135°C. Lower melting point indicates impurity.

Practical 3: Chromatography (Paper Chromatography)

• Principle: Components of a mixture travel at different rates through a stationary phase (filter paper) using a mobile phase (solvent) — based on their polarity and adsorption.
• Rf value: Rf = Distance travelled by component / Distance travelled by solvent front. Each substance has a characteristic Rf value in a given solvent.
• Application: Separate components of food dyes, ink, or plant pigments (chlorophyll separates into yellow, green, and orange-red bands).

Practical Exam Tips for Class 12 Chemistry (CBSE)

• Salt analysis viva questions are based on your observations — always record them accurately in your notebook
• Learn the colour of precipitates and gases — questions like “What is the colour of AgCl precipitate?” are common viva questions
• Show all safety precautions when writing procedures in your answer sheet — it adds to your marks
• Practise the steps at home using flowcharts — the identification process must be systematic, not random
• The internal assessment (30 marks) includes practicals (20 marks) + viva (5 marks) + project (5 marks)