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Analytical Chemistry with Professional Lab Experiments

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Complete Analytical Chemistry Lab Experiments

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Statistical Evaluation & Q-Test

Statistical evaluation of analytical data with Dean and Dixon Q-test for outlier detection using repeated weight measurements.

Required Chemicals & Equipment:

  • • Five rupee coins (5 pieces)
  • • Analytical balance (±0.0001g)
  • • Calculator for statistical analysis

Procedure:

  1. 1. Weigh each coin 5 times using analytical balance
  2. 2. Record all measurements in data table
  3. 3. Calculate mean, standard deviation, and relative standard deviation
  4. 4. Apply Q-test: Q = |suspect value – nearest value| / range
  5. 5. Compare calculated Q with critical Q value (0.710 for n=5)

Sample Calculation:

Weights: 3.85g, 3.87g, 3.86g, 3.84g, 3.92g
Mean = 3.868g
Q = |3.92 – 3.87| / (3.92 – 3.84) = 0.625
Since Q < 0.710, no outlier exists

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Glassware Calibration

Precise calibration of burette, pipette, and volumetric flask with error analysis and uncertainty calculations.

Required Equipment:

  • • 50 mL burette
  • • 25 mL pipette
  • • 250 mL volumetric flask
  • • Distilled water
  • • Analytical balance

Calibration Procedure:

  1. 1. Fill glassware with distilled water at 20°C
  2. 2. Weigh delivered water using analytical balance
  3. 3. Convert mass to volume using water density (0.9982 g/mL at 20°C)
  4. 4. Calculate percentage error: [(Actual – Nominal)/Nominal] × 100
  5. 5. Repeat measurements 5 times for statistical analysis

Error Calculation:

For 25 mL pipette:
Mass of water = 24.95g
Volume = 24.95/0.9982 = 25.00 mL
Error = [(25.00-25.00)/25.00] × 100 = 0.00%

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Standard Solution Preparation

Preparation of molar, normal, and ppm solutions of oxalic acid, NaOH, HCl, and H₂SO₄ with precise calculations.

Required Chemicals:

  • • Oxalic acid dihydrate (H₂C₂O₄·2H₂O)
  • • Sodium hydroxide pellets (NaOH)
  • • Hydrochloric acid (HCl, 37%)
  • • Sulfuric acid (H₂SO₄, 98%)
  • • Distilled water

Preparation Steps:

  1. 1. Calculate required mass/volume using molarity formula
  2. 2. Weigh solid reagents using analytical balance
  3. 3. Dissolve in small amount of distilled water
  4. 4. Transfer to volumetric flask and dilute to mark
  5. 5. Mix thoroughly and label properly

Sample Calculation (0.1M Oxalic Acid):

Molecular weight = 126.07 g/mol
For 250 mL: Mass = 0.1 × 0.25 × 126.07 = 3.15g
Weigh 3.15g oxalic acid dihydrate

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NaOH Standardization

Standardization of sodium hydroxide (secondary standard) against oxalic acid (primary standard) using acid-base titration.

Required Solutions:

  • • 0.1M Oxalic acid (primary standard)
  • • ~0.1M NaOH solution (to be standardized)
  • • Phenolphthalein indicator
  • • Distilled water

Titration Procedure:

  1. 1. Pipette 25 mL oxalic acid into conical flask
  2. 2. Add 2-3 drops phenolphthalein indicator
  3. 3. Fill burette with NaOH solution
  4. 4. Titrate until permanent pink color appears
  5. 5. Record burette readings and repeat 3 times

Calculation:

H₂C₂O₄ + 2NaOH → Na₂C₂O₄ + 2H₂O
M₁V₁/n₁ = M₂V₂/n₂
M(NaOH) = (0.1 × 25 × 2)/(V(NaOH) × 1)

🧂

Sodium Chloride Analysis

Quantitative determination of sodium chloride percentage in sample mixtures using precise acid-base titration methods.

Required Materials:

  • • Unknown NaCl sample mixture
  • • Standardized 0.1M AgNO₃ solution
  • • K₂CrO₄ indicator (5%)
  • • Distilled water

Analysis Procedure:

  1. 1. Weigh accurately 0.5-1.0g sample
  2. 2. Dissolve in 50 mL distilled water
  3. 3. Add 1 mL K₂CrO₄ indicator
  4. 4. Titrate with AgNO₃ until brick-red precipitate forms
  5. 5. Calculate NaCl percentage from titration volume

Percentage Calculation:

NaCl + AgNO₃ → AgCl + NaNO₃
% NaCl = (M × V × 58.44 × 100)/(Sample weight × 1000)
Where M = Molarity of AgNO₃, V = Volume used

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Aspirin Content Analysis

Accurate determination of aspirin content in Disprin tablets using back-titration with standardized acid-base solutions.

Required Solutions:

  • • Disprin tablets
  • • Standardized 0.1M NaOH
  • • Standardized 0.1M HCl
  • • Phenolphthalein indicator
  • • Ethanol (for dissolution)

Back-Titration Method:

  1. 1. Crush and weigh one Disprin tablet accurately
  2. 2. Add excess 0.1M NaOH (50 mL) and heat gently
  3. 3. Cool and add phenolphthalein indicator
  4. 4. Back-titrate excess NaOH with 0.1M HCl
  5. 5. Calculate aspirin content from consumed NaOH

Aspirin Calculation:

C₉H₈O₄ + NaOH → C₉H₇O₄Na + H₂O
Moles NaOH consumed = (50 × 0.1) – (V(HCl) × 0.1)
Aspirin mass = Moles × 180.16 g/mol

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Water Hardness Determination

Complexometric determination of total hardness (Ca²⁺ + Mg²⁺) in water samples using EDTA as complexing agent.

Required Reagents:

  • • Water samples (tap, well, distilled)
  • • 0.01M EDTA solution
  • • Eriochrome Black T indicator
  • • NH₃-NH₄Cl buffer (pH 10)

Complexometric Procedure:

  1. 1. Take 50 mL water sample in conical flask
  2. 2. Add 5 mL buffer solution (pH 10)
  3. 3. Add 2-3 drops Eriochrome Black T indicator
  4. 4. Titrate with EDTA until blue color appears
  5. 5. Calculate hardness as mg/L CaCO₃ equivalent

Hardness Calculation:

Hardness (mg/L as CaCO₃) = (V(EDTA) × M(EDTA) × 100.09 × 1000)/V(sample)
Where 100.09 = Molecular weight of CaCO₃

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Chloride by Mohr’s Method

Precise determination of chloride content in water samples using Mohr’s argentometric titration method with visual endpoint detection.

Required Solutions:

  • • Water samples for analysis
  • • Standardized 0.1M AgNO₃ solution
  • • 5% K₂CrO₄ indicator solution
  • • Distilled water for dilution

Mohr’s Titration Steps:

  1. 1. Take 50 mL water sample (pH 6.5-10.5)
  2. 2. Add 1 mL K₂CrO₄ indicator
  3. 3. Titrate with AgNO₃ until persistent brick-red color
  4. 4. Record endpoint volume accurately
  5. 5. Calculate chloride concentration in mg/L

Chloride Calculation:

Cl⁻ + AgNO₃ → AgCl + NO₃⁻
Chloride (mg/L) = (V(AgNO₃) × M(AgNO₃) × 35.45 × 1000)/V(sample)
Where 35.45 = Atomic weight of Cl

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Calcium in Gluconate Injection

Quantitative analysis of calcium content in pharmaceutical calcium gluconate injection using EDTA complexometric titration.

Key Calculation:

Ca²⁺ + EDTA⁴⁻ → [Ca-EDTA]²⁻
Ca content (mg/mL) = (V(EDTA) × M(EDTA) × 40.08)/V(injection)

🔶

Gravimetric Copper Analysis

Gravimetric determination of copper as cupric oxide (CuO) from unknown samples containing copper metal with precision weighing.

Gravimetric Factor:

Cu → CuO (heating in air)
% Cu = (Weight of CuO × 63.55)/(79.55 × Sample weight) × 100
Gravimetric factor = 63.55/79.55 = 0.7989

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