WAEC Chemistry Practical 2025

Good afternoon, students!
My name is Francis, and in today’s Chemistry practical class, we’ll be diving into some general Chemistry Practical questions — specifically Volumetric Analysis (Titration).

These questions are very likely to show up in WAEC, NECO, GCE, and even JAMB Chemistry Practical. So, sit back, grab your writing materials and calculator. Let’s begin!

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You can watch the full class in the video below:

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https://www.youtube.com/watch?v=X8sU3nMfqQ0

SECTION A – Titration & Volumetric Analysis

Let’s solve some popular past questions and explain the concepts behind them.

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Question 1: Calculate the Molarity of a Sodium Hydroxide Solution

Problem Statement:
Calculate the molarity of a sodium hydroxide (NaOH) solution if 25 cm³ of it neutralizes 20 cm³ of 0.1 M HCl.

Step-by-Step Solution

Balanced Equation: HCl (acid)+NaOH (base)→NaCl (salt)+H2O (water)\text{HCl (acid)} + \text{NaOH (base)} \rightarrow \text{NaCl (salt)} + \text{H}_2\text{O (water)}HCl (acid)+NaOH (base)→NaCl (salt)+H2​O (water)

This gives a 1:1 molar ratio between acid and base.

Formula Used: CA×VACB×VB=nAnB\frac{C_A \times V_A}{C_B \times V_B} = \frac{n_A}{n_B}CB​×VB​CA​×VA​​=nB​nA​​

Since it’s 1:1: CB=CA×VAVB=0.1×2025=225=0.08 mol/dm3C_B = \frac{C_A \times V_A}{V_B} = \frac{0.1 \times 20}{25} = \frac{2}{25} = 0.08 \, \text{mol/dm}^3CB​=VB​CA​×VA​​=250.1×20​=252​=0.08mol/dm3

Answer: 0.08 mol/dm³

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Question 2: Calculate Average Titre Value

Given:
Three concordant titre values:

• 22.50 cm³
• 22.60 cm³
• 22.55 cm³

Requirement:
Check if they are within the ±0.2 cm³ range.

• Difference between 22.60 and 22.50 = 0.10
• Difference between 22.60 and 22.55 = 0.05

Since they’re all within the allowed range, you can average them: 22.50+22.60+22.553=67.653=22.55 cm3\frac{22.50 + 22.60 + 22.55}{3} = \frac{67.65}{3} = 22.55 \, \text{cm}^3322.50+22.60+22.55​=367.65​=22.55cm3

Answer: 22.55 cm³

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Question 3: Best Indicator for Strong Acid + Strong Base Titration

Question:
Which indicator is suitable when titrating a strong acid with a strong base?

Answer:
You can use Methyl Orange or Phenolphthalein. Either is acceptable depending on the precise endpoint observed.

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Question 4: Why Should the Burette Be Rinsed Before Use?

Question:
Why is it important to rinse the burette with the solution it will contain?

Answer:
Rinsing the burette with the acid or base ensures that:

• The solution inside isn’t diluted with water or other residue.
• Accurate volume readings are taken.

Failure to rinse can lead to over-dilution and inaccurate results.

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Watch more educational videos and past questions: https://youtube.com/@allcbts

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More Questions Coming?

This lesson is just a snippet of what’s coming in full Chemistry Practical Tutorials on AllCBTs. You’ll master:

• Acid-base titration setups
• Choosing the right indicator
• Calculating molarity and reacting volumes
• Recording concordant titre values

Related Videos:

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Keywords

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