Describe an acid-base titration to include the use of a: (a) burette (b) volumetric pipette (c) suitable indicator

Acid–Base Titration: A Step‑by‑Step Guide

What is a Titration?

Think of a titration as a “chemical race” where two teams (acid and base) meet at the finish line. The goal is to find the exact point where they balance each other out. That point is called the equivalence point.

Equipment we’ll use

• Burette – the “pouring bottle” that delivers the base slowly.
• Volumetric pipette – the “precise measuring cup” that gives us an exact volume of the acid.
• Indicator – the “colour‑changing detective” that tells us when the race is over.

Step 1: Prepare the Acid Solution

1. Fill the volumetric pipette with \$0.100\,\text{M}\,\text{HCl}\$ (or any known acid). The pipette is calibrated to deliver exactly \$25.00\,\text{mL}\$.
2. Transfer the acid into a clean conical flask. This is our “acid pit.”

Step 2: Set Up the Burette

Fill the burette with \$0.100\,\text{M}\,\text{NaOH}\$ (our base). Make sure the tip is clear of air bubbles. The burette reads in millilitres, and we’ll record the initial volume \$V_i\$.

Step 3: Add the Indicator

Drop a few drops of phenolphthalein into the acid. It stays colourless in acid but turns pink in a basic environment. Think of it as a mood ring that changes colour when the chemistry changes.

Step 4: Run the Titration

1. Slowly open the burette valve and let the base flow into the acid.
2. Stir gently with a magnetic stirrer (or a glass rod) to mix.
3. Watch the colour. When it turns a faint pink that stays for 30 s, you’ve reached the equivalence point.
4. Close the valve and record the final volume \$V_f\$.

Step 5: Calculate the Acid Concentration

Use the formula:

\$Ca Va = Cb Vb\$

where:

• \$C_a\$ = concentration of the acid (unknown)
• \$V_a\$ = volume of acid (25.00 mL)
• \$C_b\$ = concentration of the base (0.100 M)
• \$Vb\$ = volume of base used (\$Vf - V_i\$)

Rearrange to find \$C_a\$:

\$Ca = \dfrac{Cb Vb}{Va}\$

Common Mistakes to Avoid

• Air bubbles in the burette tip – they give a false reading.
• Not stirring – leads to uneven mixing.
• Reading the meniscus at eye level – keep your eye level with the bottom of the curve.

Quick Reference Table

Fun Fact

Did you know that the first titration was performed by the ancient Greeks using vinegar and baking soda? They were essentially doing a simple acid‑base reaction to see how much soda was needed to neutralise the vinegar! 🧪