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Practice Class 9 Science Chapter 2 – Is Matter Around Us Pure? with 5 NCERT-based MCQs on concentration of solutions, mass percentage, components of solutions, solubility and the classification of mixtures.
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Chapter Information
Subject: Science
Class: 9
Chapter: Is Matter Around Us Pure?
Question Type: Multiple Choice Questions (MCQs)
Practice Set: 3
Difficulty Level: Moderate
Based On: NCERT Syllabus
Introduction
The concentration of a solution tells us about the amount of solute present in a given amount of solution. It is an important property used to compare solutions and understand their composition.
In this Practice Set 3, students will revise concentration, mass percentage, solute, solvent, solution composition and classification of mixtures through NCERT-based MCQs.
What You Will Learn
✔ Concentration of a solution
✔ Mass percentage
✔ Solute and solvent
✔ Composition of a solution
✔ Solubility
✔ Classification of mixtures
✔ Application of solution concepts
Why This Topic Is Important
Understanding the concentration of solutions is important for both conceptual and numerical questions.
Students should be able to identify the solute and solvent, calculate or interpret mass percentage, and understand how the composition of a solution changes when the amount of solute or solvent changes.
These concepts are frequently useful in NCERT-based examinations.
5 MCQs with Answers and Detailed Solutions
Q1. A solution contains 10 g of salt and 90 g of water. What is the mass percentage of salt in the solution?
A) 5%
B) 10%
C) 20%
D) 90%
Answer: B) 10%
Detailed Solution
First calculate the total mass of the solution:
Mass of solution = Mass of solute + Mass of solvent
= 10 g + 90 g
= 100 g
Now use the mass percentage formula:
Mass percentage = (Mass of solute / Mass of solution) × 100
= (10 / 100) × 100
= 10%
Therefore, the mass percentage of salt is 10%.
Exam Tip
Always calculate the total mass of solution first before applying the mass percentage formula.
Q2. A solution is prepared by dissolving 5 g of sugar in 95 g of water. What is the mass of the solvent?
A) 5 g
B) 90 g
C) 95 g
D) 100 g
Answer: C) 95 g
Detailed Solution
The solvent is the component in which the solute dissolves.
Here:
- Sugar = Solute
- Water = Solvent
The question states that 95 g of water is used. Therefore, the mass of the solvent is 95 g.
Exam Tip
Identify the substance that does the dissolving before deciding which component is the solvent.
Q3. Which expression correctly represents the mass percentage of a solution?
A) (Mass of solvent / Mass of solution) × 100
B) (Mass of solute / Mass of solution) × 100
C) (Mass of solution / Mass of solute) × 100
D) (Mass of solute + Mass of solvent) × 100
Answer: B) (Mass of solute / Mass of solution) × 100
Detailed Solution
Mass percentage tells us what percentage of the total mass of the solution is contributed by the solute.
Therefore:
Mass percentage = (Mass of solute / Mass of solution) × 100
Since:
Mass of solution = Mass of solute + Mass of solvent
this formula can be used to calculate the percentage by mass of the solute.
Exam Tip
For mass percentage, remember: solute goes on top and solution goes below.
Q4. Which of the following pairs correctly identifies the solute and solvent in a sugar solution?
A) Sugar – solvent; water – solute
B) Sugar – solute; water – solvent
C) Sugar – solution; water – solute
D) Sugar – solvent; water – solution
Answer: B) Sugar – solute; water – solvent
Detailed Solution
When sugar is added to water, sugar dissolves in water.
Therefore:
- Sugar → Solute
- Water → Solvent
Together, they form a sugar solution, which is a homogeneous mixture.
Exam Tip
The substance being dissolved is the solute; the substance in which it dissolves is the solvent.
Q5. Which of the following is a heterogeneous mixture?
A) Salt solution
B) Sugar solution
C) Air
D) Soil
Answer: D) Soil
Detailed Solution
A heterogeneous mixture does not have a uniform composition throughout.
Soil contains different components such as sand, clay, minerals and organic matter. These components are not uniformly distributed.
Salt solution, sugar solution and air are generally treated as homogeneous mixtures in this context.
Exam Tip
For common examples, remember soil → heterogeneous mixture and salt solution → homogeneous mixture.
Important Formulas & Concepts
1. Mass Percentage
The mass percentage of a solute in a solution is:
Mass percentage = (Mass of solute / Mass of solution) × 100
2. Mass of Solution
Mass of solution = Mass of solute + Mass of solvent
3. Solute
The substance that gets dissolved in a solution is called the solute.
4. Solvent
The substance in which the solute dissolves is called the solvent.
5. Solution
A solution is a homogeneous mixture of two or more components.
6. Homogeneous Mixture
A mixture having a uniform composition throughout is called a homogeneous mixture.
7. Heterogeneous Mixture
A mixture having a non-uniform composition is called a heterogeneous mixture.
Related Practice Questions
Q1. What is mass percentage?
Q2. How do you calculate the mass of a solution?
Q3. What is the difference between solute and solvent?
Q4. Why is soil considered a heterogeneous mixture?
Q5. Is air a mixture or a pure substance?
Mini Quiz Challenge
Try answering these questions within 60 seconds.
Q1. A solution contains 20 g salt and 80 g water. Its mass percentage of salt is:
A) 10%
B) 20%
C) 25%
D) 80%
Q2. In a sugar-water solution, water is the:
A) Solute
B) Solvent
C) Residue
D) Colloid
Q3. Which formula gives mass percentage?
A) Mass of solution / Mass of solute × 100
B) Mass of solute / Mass of solution × 100
C) Mass of solvent / Mass of solute × 100
D) Mass of solute + Mass of solvent
Q4. Which is a heterogeneous mixture?
A) Air
B) Salt solution
C) Soil
D) Sugar solution
Q5. If 15 g of solute is mixed with 85 g of solvent, the mass of the solution is:
A) 70 g
B) 85 g
C) 100 g
D) 115 g
Exam Tips
✔ Memorise the mass percentage formula.
✔ Always calculate the total mass of solution correctly.
✔ Do not confuse solute and solvent.
✔ Practise simple numerical questions based on mass percentage.
✔ Remember common examples of homogeneous and heterogeneous mixtures.
Quick Revision Notes
✔ Mass percentage = (Mass of solute / Mass of solution) × 100
✔ Mass of solution = Mass of solute + Mass of solvent
✔ Solute: Substance that gets dissolved.
✔ Solvent: Substance in which the solute dissolves.
✔ Solution: Homogeneous mixture.
✔ Soil: Heterogeneous mixture.
✔ Air: Homogeneous mixture of gases.
✔ Sugar-water and salt-water solutions are homogeneous mixtures when the substances are completely dissolved.
Common Mistakes Students Make
❌ Using the mass of solvent instead of the mass of solution in the mass percentage formula.
❌ Forgetting to add the mass of solute and solvent.
❌ Interchanging solute and solvent.
❌ Writing the percentage formula incorrectly.
❌ Assuming that every mixture is heterogeneous.
❌ Treating a solution as a pure substance.
Key Takeaways
✔ Concentration describes the amount of solute present in a solution.
✔ Mass percentage is an important way of expressing concentration.
✔ The total mass of a solution is the sum of the masses of its solute and solvent.
✔ The solute dissolves in the solvent.
✔ A solution is a homogeneous mixture.
✔ Soil is an example of a heterogeneous mixture.
✔ Correct identification of solute and solvent is important in numerical questions.
FAQs
Q. What is mass percentage?
Answer:
Mass percentage is the mass of solute present in 100 parts by mass of the solution.
Q. What is the formula for mass percentage?
Answer:
Mass percentage = (Mass of solute / Mass of solution) × 100
Q. How is the mass of a solution calculated?
Answer:
Mass of solution = Mass of solute + Mass of solvent
Q. What is the solute in a sugar solution?
Answer:
Sugar is the solute because it dissolves in water.
Q. What is the solvent in a sugar solution?
Answer:
Water is the solvent because sugar dissolves in water.
Q. Why is soil a heterogeneous mixture?
Answer:
Soil contains different components that are not uniformly distributed throughout the mixture.
Conclusion
Class 9 Science Chapter 2 – Is Matter Around Us Pure? focuses on concentration, mass percentage, solute, solvent and classification of mixtures.
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