Perform experiments on volumetric analysis

Before performing any titration, you must know the purpose of each piece of glassware:

• Burette – a long glass tube with graduated markings used to deliver measured volumes of the titrant (the solution of known concentration)
• Pipette – used to measure an exact volume of the analyte (the unknown solution) into a conical flask
• Volumetric flask – used to prepare standard solutions of precise concentration
• Conical flask (Erlenmeyer flask) – holds the analyte during titration; its shape allows easy swirling without spilling
• Funnel – helps pour solutions into the burette without spilling
• Wash bottle – contains distilled water for rinsing equipment
• Beaker – for general mixing and holding solutions

• Titrant – the solution of known concentration in the burette
• Analyte (or titrand) – the unknown solution being analyzed
• Standard solution – a solution of precisely known concentration
• Equivalence point – the moment when the acid and base have completely reacted (the reaction is complete)
• Indicator – a substance (like phenolphthalein or methyl orange) that changes color near the equivalence point to show the reaction is finished

In the chemistry laboratory at Form 3 level, you will typically perform neutralization titrations using these substances:

Follow these steps carefully to obtain accurate results:

1. Rinse the burette with distilled water, then with a small amount of the titrant solution
2. Fill the burette with the titrant (known concentration) and record the initial reading
3. Pipette a precise volume (usually 25 cm³) of the analyte into a conical flask
4. Add 2-3 drops of a suitable indicator (phenolphthalein for acid-base titrations)
5. Perform the titration by slowly adding the titrant from the burette while gently swirling the flask
6. Watch for the endpoint – the color changes sharply (e.g., from colorless to pink for phenolphthalein)
7. Record the final burette reading and calculate the volume of titrant used
8. Repeat the titration at least twice to ensure consistent results

Problem: 25.0 cm³ of an unknown HCl solution is titrated with 0.10 M NaOH. The average volume of NaOH used is 24.0 cm³. Calculate the molarity of the HCl solution.

Solution:

Step 1: Write the balanced equation

$HCl + NaOH \rightarrow NaCl + H_2O$

The molar ratio is 1:1 (one mole of HCl reacts with one mole of NaOH).

Step 2: Apply the formula

At the equivalence point:

$M_A V_A = M_B V_B$

Where:

• $M_A$ = molarity of HCl (unknown)
• $V_A$ = volume of HCl = 25.0 cm³
• $M_B$ = molarity of NaOH = 0.10 M
• $V_B$ = volume of NaOH = 24.0 cm³

Step 3: Calculate

$M_A = \frac{M_B \times V_B}{V_A}$

$M_A = \frac{0.10 \times 24.0}{25.0} = 0.096 \text{ M}$

The concentration of the unknown HCl solution is 0.096 mol/dm³.

• Always wear safety goggles and a laboratory coat
• Handle acids and bases with care – they can cause burns
• If acid or base spills on skin, rinse immediately with plenty of water
• Never eat or drink in the laboratory
• Dispose of chemicals properly as instructed by your teacher

In Tanzania, volumetric analysis is used in water quality testing at municipal water treatment plants in cities like Dar es Salaam and Arusha. Technicians use titration to measure the acidity of water and determine how much chlorine or lime must be added to make the water safe for drinking. This ensures that the water supplied to households meets safety standards and prevents waterborne diseases.