Analytical Chemistry — Standard Solutions & Titration

Cameroon GCE Ordinary Level Notes (Based on National Curriculum)

Standard Solution

Definition

A standard solution is one whose concentration is accurately known. It is usually prepared from a pure substance known as a primary standard.

Preparation Steps (just 03 steps)

Weigh the solid accurately using a balance.
Dissolve the solid in a beaker using distilled water.
Transfer the solution into a volumetric flask and rinse and Make up to the mark with distilled water.

Use a primary standard that is pure, stable, and non-hygroscopic (e.g., anhydrous Na₂CO₃).

Titration

Definition

Titration is a method used to determine the concentration of an unknown solution by reacting it with a standard solution until the end-point is reached.

Procedure

Rinse and set up burette, pipette, and conical flask properly.
Pipette a measured volume of the unknown solution into the flask and add a few drops of an indicator.
Fill the burette with the standard solution and record the initial reading.
Add titrant gradually while swirling the flask until the indicator changes colour.
Record the final reading and calculate the titre value.
Repeat until you obtain at least three concordant readings.

Safety: Always wear goggles.

Equipment Used in Titration

Burette

Pipette

Conical Flask

Stand & Clamp

Volumetric Flask

Common Indicators

Indicator	Colour Change	Used In
Phenolphthalein	Colourless → Pink	Strong acid vs strong base
Methyl Orange	Red → Yellow	Strong acid vs weak base
Bromothymol Blue	Yellow → Blue	Neutral titrations
KMnO₄ (self-indicator)	Colourless → Faint pink	Redox titrations

Summary of Key Points

A standard solution has a known concentration.
Primary standards must be pure, stable, and non-hygroscopic.
Titration is used to find unknown concentrations using accurate volumetric apparatus.
Indicators show the end point through colour change.
Always rinse equipment properly and take readings at eye level.

Student Review Questions & Answers

1. Define a standard solution.
A solution whose concentration is accurately known.

2. Mention any two properties of a primary standard.
It must be pure and non-hygroscopic.

3. Name three apparatus used in titration.
Burette, pipette, conical flask.

4. Why is a white tile used during titration?
To clearly observe the colour change at the end point.

5. Give one example of an indicator used in acid-base titration.
Phenolphthalein.