ALLCBTs

Chemistry Practical Past Questions.

Published on Jul 28, 2025 • Education

Introduction

Good afternoon everyone, and welcome to today’s chemistry tutorial.
In this session, we’ll explore general questions in practical chemistry taken from past WAEC, NECO, and JAMB examinations. The focus will be on indicators, laboratory reagents, salts, and common chemical tests.

Mastering these questions helps students prepare for practical exams and theory papers where hands-on lab knowledge is tested.

You can watch the full class in the video below:

Question 1: Color of Litmus in Alkaline Solution

Question:
The color of litmus in an alkaline solution is:

• A) Red
• B) Green
• C) Blue
• D) Yellow

Explanation

Litmus paper acts as an indicator:

• In acidic solutions, litmus turns red.
• In alkaline (basic) solutions, litmus turns blue.

Correct Answer: C) Blue

Question 2: Test for Carbon Dioxide

Question:
Which of the following is used to test for the presence of carbon dioxide?

• A) Blue litmus paper
• B) Lime water
• C) Red litmus paper
• D) Potassium dichromate

Explanation

The standard test for carbon dioxide (CO₂) is lime water. When CO₂ is bubbled through lime water, it turns milky due to the formation of calcium carbonate.

Correct Answer: B) Lime water

Question 3: Efflorescent Salts

Question:
Which of the following salts is efflorescent?

• A) Magnesium chloride
• B) Sodium trioxocarbonate decahydrate (washing soda)
• C) Calcium chloride
• D) Copper(II) tetraoxosulphate(VI) pentahydrate

Explanation

Efflorescent salts lose water of crystallization when exposed to air. Sodium trioxocarbonate decahydrate (Na₂CO₃·10H₂O) is a classic example.

Correct Answer: B) Sodium trioxocarbonate decahydrate

Question 4: Best Drying Agent for Hydrogen Gas

Question:
The best drying agent for hydrogen gas is:

• A) Calcium chloride
• B) Concentrated H₂SO₄
• C) Anhydrous copper(II) sulphate
• D) Sodium chloride

Explanation

Calcium chloride is an effective drying agent for gases like hydrogen because it removes moisture without reacting with the gas.

Correct Answer: A) Calcium chloride

Question 5: Appearance of Iodine Crystals

Question:
What is the appearance of iodine crystals?

• A) White solid
• B) Reddish-brown solution
• C) Gray solid with a shiny surface
• D) Blue-black solid

Explanation

Iodine crystals are gray solids with a shiny (lustrous) surface. They produce a purple vapor when heated.

Correct Answer: C) Gray solid with shiny surface

Question 6: Reagent for Identifying Starch

Question:
Which reagent is used to identify starch in a solution?

• A) Fehling’s solution
• B) Benedict’s solution
• C) Iodine solution
• D) Lime water

Explanation

Iodine solution reacts with starch to give a blue-black coloration, confirming the presence of starch.

Correct Answer: C) Iodine solution

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

Conclusion

Practical chemistry focuses on hands-on laboratory techniques and chemical tests. Understanding indicators like litmus, efflorescent salts, and reagents such as iodine and lime water is essential for exam success. With consistent practice of past questions, students can easily handle the practical aspect of their chemistry exams.

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Keywords

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