PRACTICAL CHEMISTRY

Practical Chemistry Lecture - 2025 Core Areas

1. Volumetric Analysis (Titration)

Acid-base titrations using reagents like HCl, NaOH, or similar.

Key objectives:

• Determination of concentrations in mol/dm³ and g/dm³
• Calculation of water of crystallization
• Titration calculations: stoichiometry, molarity, and volume

Titration Table Example

Reading	Rough (cm³)	1st Titration (cm³)	2nd Titration (cm³)	3rd Titration (cm³)
Volume of HCl used	12.3	12.1	12.0	12.2

Average volume of acid used:

(12.1 + 12.0 + 12.2) / 3 = 12.1 cm³

Titration Calculations

1. Molarity of NaOH:

Use formula: M₁V₁ = M₂V₂

Example: HCl 0.1M, V=12.1cm³, NaOH V=25cm³ → M₂ = (0.1 × 12.1)/25 = 0.0484 M

2. Molarity in g/dm³:

Molar mass NaOH = 40 g/mol → g/dm³ = 0.0484 × 40 = 1.936 g/dm³

3. Mole ratio calculation:

Reaction: HCl + NaOH → NaCl + H₂O, ratio 1:1, confirms stoichiometry

4. Percentage purity:

Sample mass = 2g, titrated moles = 0.00121 mol, expected = 0.00125 → % purity = (0.00121/0.00125)×100 ≈ 96.8%

5. Water of crystallization:

CuSO₄·xH₂O: mass lost on heating = 9.6g, original sample = 25g → x = (9.6/18) ÷ (15.4/159.6) ≈ 5

2. Qualitative Analysis - Test for Ions

Identify cations and anions, record observations and inferences.

Cations Test Table

Test	Procedure	Observation	Inference
Na⁺	Flame test	Yellow flame	Presence of Na⁺
Ca²⁺	NaOH solution	White precipitate	Presence of Ca²⁺
Cu²⁺	Ammonia solution	Blue solution	Presence of Cu²⁺
Zn²⁺	NaOH then heat	White precipitate soluble in excess	Zn²⁺ confirmed
Fe³⁺	NaOH solution	Red-brown precipitate	Presence of Fe³⁺

Anions Test Table

Anion	Reagent	Observation	Inference
Cl⁻	AgNO₃	White precipitate	Chloride present
SO₄²⁻	BaCl₂ + HCl	White precipitate	Sulfate present
CO₃²⁻	HCl	Effervescence, CO₂ evolved	Carbonate present
NO₃⁻	FeSO₄ + conc. H₂SO₄	Brown ring at interface	Nitrate present
PO₄³⁻	Ammonium molybdate + HNO₃	Yellow precipitate	Phosphate present

3. Functional Group Tests

• Alcohols: Orange color with acidified potassium dichromate, reduction to green.
• Alkanoic acids: Effervescence with carbonates (CO₂ evolved)
• Alkenes: Decolorization of bromine water
• Reducing sugars: Brick-red precipitate with Fehling’s solution

4. General Experiments

• Rate of reaction: Measure volume of gas evolved over time
• Thermochemistry: Heat of neutralization or reaction measurement
• Separation techniques: Filtration, crystallization
• Alternative to practical: Use graphs, data, or scenarios

Key Skills Required

• Accurate volume and mass measurements
• Observation and recording color changes, precipitates, gas evolution
• Precise calculation of molarity, concentration, % purity, and water of crystallization
• Understanding of stoichiometry and mole ratios in titration
• Identification of cations, anions, and functional groups