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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 by mass percentage, mass by volume percentage, homogeneous mixtures and components of solutions.
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Chapter Information
Subject: Science
Class: 9
Chapter: Is Matter Around Us Pure?
Question Type: Multiple Choice Questions (MCQs)
Practice Set: 12
Difficulty Level: Moderate
Based On: NCERT Syllabus
Introduction
The concentration of a solution describes the relative amount of solute present in a given amount of solution. It helps us compare solutions and understand whether a solution is dilute or concentrated.
According to the NCERT Class 9 Science chapter, concentration can be expressed using different methods, including mass by mass percentage and mass by volume percentage.
This Practice Set 12 focuses on the concentration of solutions, percentage composition, solute, solvent and homogeneous mixtures.
What You Will Learn
✔ Concentration of a solution
✔ Mass by mass percentage
✔ Mass by volume percentage
✔ Solute and solvent
✔ Homogeneous mixtures
✔ Percentage composition of solutions
Why This Topic Is Important
The concept of concentration is important because it allows students to describe how much solute is present in a solution quantitatively.
Students should understand the difference between mass by mass percentage and mass by volume percentage and identify the solute and solvent correctly.
5 MCQs with Answers and Detailed Solutions
Q1. A solution contains 20 g of salt and 80 g of water. What is the mass by mass percentage of salt in the solution?
A) 10%
B) 20%
C) 25%
D) 80%
Answer: B) 20%
Detailed Solution
Mass by mass percentage is calculated using:
Mass percentage = (Mass of solute / Mass of solution) × 100
Mass of salt = 20 g
Mass of water = 80 g
Mass of solution = 20 + 80 = 100 g
Therefore:
Mass percentage = (20 / 100) × 100 = 20%
Hence, the correct answer is B) 20%.
Exam Tip
Always remember:
Mass of solution = Mass of solute + Mass of solvent
Q2. Which formula is used to calculate mass by 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
Answer: B) (Mass of solute / Mass of solution) × 100
Detailed Solution
Mass by mass percentage tells us the mass of solute present in 100 parts by mass of the solution.
The formula is:
Mass by mass percentage = (Mass of solute / Mass of solution) × 100
Therefore, the correct answer is B.
Exam Tip
Remember:
Mass % = Mass of solute ÷ Mass of solution × 100
Q3. A solution contains 10 g of glucose dissolved in 90 g of water. What is the mass by mass percentage of glucose?
A) 5%
B) 10%
C) 20%
D) 90%
Answer: B) 10%
Detailed Solution
Mass of glucose = 10 g
Mass of water = 90 g
Therefore:
Mass of solution = 10 + 90 = 100 g
Using:
Mass percentage = (Mass of solute / Mass of solution) × 100
= (10 / 100) × 100
= 10%
Therefore, the correct answer is B) 10%.
Exam Tip
When the total mass of the solution is 100 g, the mass of solute in grams directly represents the mass percentage.
Q4. A solution contains 5 g of salt dissolved in 100 mL of solution. What is its mass by volume percentage?
A) 2%
B) 5%
C) 10%
D) 20%
Answer: B) 5%
Detailed Solution
Mass by volume percentage is calculated using:
Mass by volume percentage = (Mass of solute / Volume of solution) × 100
Mass of salt = 5 g
Volume of solution = 100 mL
Therefore:
Mass by volume percentage = (5 / 100) × 100 = 5%
Hence, the correct answer is B) 5%.
Exam Tip
For mass by volume percentage, use:
Mass of solute ÷ Volume of solution × 100
Q5. In a solution of sugar in water, which statement is correct?
A) Sugar is the solvent and water is the solute
B) Water is the solute and sugar is the solvent
C) Sugar is the solute and water is the solvent
D) Both sugar and water are solutes
Answer: C) Sugar is the solute and water is the solvent
Detailed Solution
In a sugar solution, sugar dissolves in water.
Therefore:
- Sugar = Solute
- Water = Solvent
The resulting sugar solution is a homogeneous mixture when the sugar completely dissolves.
Hence, the correct answer is C) Sugar is the solute and water is the solvent.
Exam Tip
Ask yourself:
Which substance is being dissolved? → Solute
Which substance dissolves it? → Solvent
Important Concepts
1. Concentration of a Solution
Concentration tells us the amount of solute present in a given amount of solution.
A solution with relatively more solute is generally described as more concentrated than one with less solute under comparable conditions.
2. Mass by Mass Percentage
The mass by mass percentage of a solution is:
Mass by mass percentage = (Mass of solute / Mass of solution) × 100
3. Mass by Volume Percentage
The mass by volume percentage of a solution is:
Mass by volume percentage = (Mass of solute / Volume of solution) × 100
4. Solute
The substance that gets dissolved is called the solute.
5. Solvent
The substance in which the solute dissolves is called the solvent.
6. Solution
A solution is a homogeneous mixture of two or more substances.
Related Practice Questions
Q1. What is concentration of a solution?
Q2. How is mass by mass percentage calculated?
Q3. How is mass by volume percentage calculated?
Q4. What is a solute?
Q5. What is a solvent?
Mini Quiz Challenge
Try answering these questions within 60 seconds.
Q1. A solution contains 15 g salt and 85 g water. What is the mass percentage of salt?
A) 10%
B) 15%
C) 20%
D) 85%
Q2. The total mass of a solution is equal to:
A) Mass of solute only
B) Mass of solvent only
C) Mass of solute + mass of solvent
D) Mass of solute − mass of solvent
Q3. What is the mass by volume percentage of a solution containing 10 g solute in 200 mL solution?
A) 2%
B) 5%
C) 10%
D) 20%
Q4. The substance that gets dissolved in a solution is called:
A) Solvent
B) Solute
C) Suspension
D) Colloid
Q5. Which type of mixture is a completely dissolved salt solution?
A) Heterogeneous mixture
B) Homogeneous mixture
C) Suspension
D) Pure substance
Exam Tips
✔ Learn the formulas for mass by mass percentage and mass by volume percentage.
✔ Always calculate the total mass of solution before finding mass percentage.
✔ Remember that the solute is the substance that gets dissolved.
✔ The solvent is the substance in which the solute dissolves.
✔ A completely dissolved salt solution is a homogeneous mixture.
✔ Carefully distinguish between mass of solution and volume of solution.
Quick Revision Notes
✔ Concentration: Amount of solute present in a given amount of solution.
✔ Mass by mass percentage: (Mass of solute / Mass of solution) × 100.
✔ Mass by volume percentage: (Mass of solute / Volume of solution) × 100.
✔ Solute: Substance that gets dissolved.
✔ Solvent: Substance in which the solute dissolves.
✔ Solution: Homogeneous mixture.
✔ Mass of solution = Mass of solute + Mass of solvent.
Common Mistakes Students Make
❌ Using the mass of solvent instead of the mass of solution in the mass percentage formula.
❌ Confusing mass by mass percentage with mass by volume percentage.
❌ Forgetting to add the masses of solute and solvent.
❌ Confusing solute with solvent.
❌ Using the volume of solvent instead of the volume of solution for mass by volume percentage.
Key Takeaways
✔ Concentration describes the amount of solute present in a solution.
✔ Mass by mass percentage uses the mass of solute and total mass of solution.
✔ Mass by volume percentage uses the mass of solute and volume of solution.
✔ The total mass of a solution is the sum of the masses of solute and solvent.
✔ The solute dissolves in the solvent.
✔ A completely dissolved salt solution is a homogeneous mixture.
FAQs
Q. What is mass by mass percentage?
Answer:
Mass by mass percentage is the mass of solute present in 100 parts by mass of the solution.
Formula:
Mass % = (Mass of solute / Mass of solution) × 100
Q. What is mass by volume percentage?
Answer:
Mass by volume percentage is the mass of solute present in 100 parts by volume of the solution.
Formula:
Mass by volume % = (Mass of solute / Volume of solution) × 100
Q. What is the difference between solute and solvent?
Answer:
The solute is the substance that gets dissolved, while the solvent is the substance in which the solute dissolves.
Q. How is the total mass of a solution calculated?
Answer:
The total mass of a solution is calculated by adding the mass of the solute and the mass of the solvent.
Q. Is a salt solution homogeneous?
Answer:
Yes. A completely dissolved salt solution is a homogeneous mixture because its composition is uniform throughout.
Conclusion
Class 9 Science Chapter 2 – Is Matter Around Us Pure? focuses on the important concepts of concentration, mass percentage, mass by volume percentage, solute, solvent and homogeneous solutions.
Understanding these concepts and applying the correct formulas helps students solve numerical and conceptual questions related to solutions accurately.
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