Students can practice the best Class 9 Science MCQ and Class 9 Science Exploration Chapter 5 MCQ Online Test with Answers, Exploring Mixtures and Their Separation for exam preparation.
Class 9 Science Chapter 5 Exploring Mixtures and Their Separation MCQ
Exploring Mixtures and Their Separation MCQ
Class 9 Science Chapter 5 MCQ Online Test
Question 1.
Which of the following is the best example of a homogeneous mixture?
A. Muddy water
B. Oil and water
C. Sugar solution
D. Sand and iron filings
Answer:
(C) Sugar solution is a homogeneous mixture because the solute particles are uniformly distributed throughout the solvent and the composition remains the same in every part of the solution.
Question 2.
A student prepares two mixtures, P and Q. In mixture P, the first and last drop taken from the container have the same composition. In mixture Q, the lower layer contains more solid particles than the upper layer after some time. Which statement is correct?
A. Both P and Q are homogeneous mixtures
B. P is homogeneous, and Q is heterogeneous
C. P is heterogeneous, and Q is homogeneous
D. Both P and Q are heterogeneous mixtures
Answer:
(B) Mixture P shows uniform composition, which is the main property of a homogeneous mixture. Mixture Q shows a non-uniform distribution of particles, so it is a heterogeneous mixture.
Question 3.
The image shows two solutions.
Based on their appearance, which of the following correctly differentiates a homogeneous mixture from a heterogeneous mixture?
A. Mixture 2 is homogeneous as it has two layers.
B. Mixture 1 is homogeneous as its components is uniform throughout.
C. Mixture 2 is heterogeneous as it has liquid components.
D. Mixture 1 is heterogeneous as its components are not visible from the naked eye.
Answer:
(B) Mixture 1 is homogeneous as its components is uniform throughout and thus has no separate layers.
Question 4.
A student made four solutions using different quantities of water and blue ink. The quantities are listed in the table.
| Solution | Volume of Ink (ml) | Volume of Water (ml) |
| 1 | 25 | 200 |
| 2 | 10 | 100 |
| 3 | 15 | 50 |
| 4 | 50 | 250 |
Which solution has the least concentration with the lightest blue colour?
A. Solution 4
B. Solution 3
C. Solution 2
D. Solution 1
Answer:
(C) Among the given solutions, solution 2 has the least concentration with lightest blue colour. The solution with the largest amount of water (solvent) and the smallest amount of ink (solute) will have the lowest concentration.
Question 5.
A solution is prepared by dissolving 20 g of a solute in 180 g of water. The mass by mass percentage of the solution is calculated by a student as follows: \(\left(\frac{20}{180}\right) \times 100 \) =11.11%. What is the error in this calculation?
A. The calculation is correct.
B. The mass of the solvent should be used in the denominator, not the mass of the solution.
C. The mass of the solution is 200 g, so the correct denominator is 200 g.
D. The percentage should be calculated as \(\left(\frac{180}{200}\right) \times 100 \)
Answer:
(C) The mass of the solution is 200 g, so the correct denominator is 200 g.
Mass by mass percentage of a solution
= \(\frac{\text { Mass of solute }}{\text { Total mass of solution }} \times 100 \)
Here, total mass of solution = 20g + 180g = 200g, not 180 g (which is only the solvent’s mass).
Question 6.
A solution contains 30 g of common salt in 270 g of water. The concentration of the solution is
A. 500%
B. 50%
C. 10%
D. 80%
Answer:
(C) The concentration of solution
= \(\frac{\text { Mass of solute }}{\text { Total mass of solution }} \times 100 \)
Mass of common salt (solute) = 30 g
Mass of water = 270 g
Mass of solution =30 + 270 = 300 g
∴ Concentration of solution = \(\frac{30}{300} \) x 100 =10%
Question 7.
Which statement correctly explains why a cold soft drink fizzes more than a warm soft drink?
A. Gases are more soluble in liquids at higher temperature
B. Gases are less soluble in liquids at lower temperature
C. Gases are more soluble in liquids at lower temperature
D. Temperature does not affect gas solubility
Answer:
(C) The solubility of gases in liquids generally decreases with increase in temperature. Therefore, a cold soft drink holds more dissolved carbon dioxide, which escapes as fizz when opened.
Question 8.
A student observes that 35 g of a salt dissolves completely in 100 g of water at 30°C, but when more salt is added at the same temperature, the extra amount remains undissolved. Which conclusion is most appropriate?
A. The solution is unsaturated and can still dissolve more solute
B. The solution is saturated at 30°C because it has dissolved the maximum amount possible at that temperature
C. The solubility of the salt decreases when more solute is added
D. The undissolved salt proves that the solvent has changed chemically
Answer:
(B) Solubility is the maximum amount of solute that can be dissolved in a fixed amount of solvent at a given temperature. Since 35 g dissolves completely at 30°C and any additional salt remains undissolved at the same temperature, the solution has already reached its maximum dissolving capacity. Therefore, it is a saturated solution at 30°C.
Question 9.
A student wants to obtain pure crystals of copper sulphate from its aqueous solution. Which method should be used and why?
A. Distillation, because water evaporates first
B. Crystallisation, because solubility changes with temperature
C. Filtration, because crystals can pass through filter paper
D. Sublimation, because copper sulphate changes directly into vapour
Answer:
(B) Crystallisation is based on the difference in solubility of a solid in a solvent at different temperatures. On cooling a hot saturated solution, pure crystals separate out.
Question 10.
A saturated solution of a salt is prepared at 70°C and then cooled to 30°C. A large amount of crystals is obtained. Which conclusion is most appropriate?
A. The solubility of the salt increased on cooling
B. The solubility of the salt decreased on cooling, so excess solute crystallised out
C. Cooling converted the dissolved salt into a new substance
D. The solvent reacted chemically with the salt during cooling
Answer:
(B) During crystallisation, when a hot saturated solution is cooled, the solubility of most solid solutes decreases relative to the amount already dissolved, so the excess solute can no longer remain dissolved in solution and separates out as crystals.
Question 11.
Which of the following situations would require fractional distillation instead of simple distillation?
A. Separation of salt from seawater
B. Separation of camphor from sand
C. Separation of two miscible liquids having very close boiling points
D. Separation of iron filings from sulphur
Answer:
(C) Fractional distillation is used when the boiling points of the liquids are close to each other, generally when the difference is less than about 25°C. In such cases, simple distillation does not give efficient separation.
Question 12.
In the distillation setup shown, a student starts heating a mixture of acetone and water. After some time, liquid begins to collect in the conical flask while most of the water still remains in the distillation flask. Which of the following best explains this observation?
A. Acetone is collected first because it is heavier than water and therefore moves faster through the condenser
B. Acetone is collected first because it has a lower boiling point than water, so it vaporises earlier and then condenses in the water-cooled condenser
C. Water is collected first because it is present in larger amount and evaporates before acetone
D. Both acetone and water always vapourise and condense in exactly the same proportion during distillation
Answer:
(B) In distillation, separation takes place on the basis of difference in boiling points. Acetone has a much lower boiling point than water, so on heating it vapourises first.
Question 13.
Which precaution is essential while performing paper chromatography?
A. The sample spot must be dipped inside the solvent initially
B. The solvent level should be above the sample spot
C. The solvent level should be below the sample spot at the start
D. The paper must be completely immersed in the solvent
Answer:
(C) In paper chromatography, the solvent level should remain below the sample spot initially. If the spot is dipped in solvent, the sample may dissolve directly into the solvent instead of moving upward properly with capillary action.
Question 14.
Consider the following list of mixtures and the method selected by four students.
| Student | Mixture | Method Chosen |
| Student 1 | Acetone + water | Distillation |
| Student 2 | Different dyes in black ink | Paper chromatography. |
| Student 3 | Hot saturated copper sulphate solution | Crystallisation |
| Student 4 | Petrol and kerosene | Simple distillation |
Which student has selected an inappropriate method?
A. Student 1
B. Student 2
C. Student 3
D. Student 4
Answer:
(D) Petrol and kerosene are liquids with relatively close boiling points, so fractional distillation is more suitable than simple distillation. The other three students have selected the correct methods for the given mixtures.
Question 15.
Which of the following mixtures is best separated by a separating funnel rather than by filtration or evaporation?
A. Common salt and water
B. Sand and water
C. Kerosene and water
D. Copper sulphate solution
Answer:
(C) A separating funnel is used to separate immiscible liquids based on a difference in density. Kerosene and water do not mix and form two layers, so this method is most suitable. The other mixtures require different methods.
Question 16.
What will be observed when a mixture of iodine and salt is heated in a China dish?
A. No change in the China dish is observed.
B. Salt is left behind in the China dish.
C. Iodine is left behind in the China dish.
D. The mixture starts melting.
Answer:
(B) On heating, iodine sublimes (changes directly from solid to vapour) while salt does not sublime and remains as residue in the china dish.
Question 17.
Four samples are given in the table. Which of the following is not an example of suspension? (Competency-Based Question)
| Sample | Component A | Component B |
| A. | Chalk powder | Water |
| B. | Sand | Water |
| C. | Dust particles | Air |
| D. | Ink | Water |
Answer:
(D) A suspension is a heterogeneous mixture in which the solute particles do not dissolve, but remain suspended throughout the bulk of the medium. So, among the given samples, the mixture of ink and water is not an example of suspension because they form a homogeneous mixture.
Question 18.
A student crushed a piece of chalk and mixed the chalk powder in 1oo ml water. The water appeared white and cloudy. After some time, the particles settled at the bottom of the container. She claims that the mixture is a suspension. What justifies her claim?
A. The particles of chalk form a separate layer.
B. The particles of chalk are uniformly distributed in water.
C. The particles of chalk are visible through the naked eye.
D. The particles mix completely with water.
Answer:
(C) The chalk particles are settled at the bottom of the container and are visible through the naked eye; thus, it is a suspension.
Question 19.
Four test tubes P, Q, R, and S contain the following substances: (Competency-Based Question)
Test tube P: a mixture of iron filings and sulphur powder.
Test tube Q: A mixture of fat in milk.
Test tube R: copper sulphate solution.
Test tube S: Chalk powder mixed in water.
A student has to check the type of solution or mixture of the above test tubes. Which test tube(s) contains colloid and suspension, respectively?
A. Only test tubes Q and S, respectively
B. Only test tube S
C. Test tube P and test tube R
D. Test tube P and test tube S
Answer:
(A) Test tube Q (fat in milk) is a colloid, and test tube S (chalk powder in water) is a suspension.
Question 20.
A teacher gives three mixtures X, Y, and Z.
X shows no Tyndall effect and remains uniform
Y shows Tyndall effect and does not settle
Z shows Tyndall effect and settles on standing. Which option correctly identifies them?
A. X = Solution, Y = Colloid, Z = Suspension
B. X = Colloid, Y = Suspension, Z = Solution
C. X = Suspension, Y = Solution, Z = Colloid
D. X = Solution, Y = Suspension, Z = Colloid
Answer:
(A) X is a solution because it does not scatter light and remains uniform
Y is a colloid because it scatters light but does not settle
Z is a suspension because it scatters light and settles on standing. Thus, option A is correct.
Question 21.
Tina passes light beams through two liquid mixtures in separate glasses as shown in the picture.
Based on the behaviour of the light beam, what are liquids 1 and 2? (Competency-Based Question)
| Liquid 1 | Liquid 2 |
| A Solution | Colloid |
| B Colloid | Suspension |
| C Suspension | Solution |
| D Suspension | Colloid |
Answer:
(A) Liquid 1.. Solution and Liquid 2- Colloid. In liquid 1, the light beam passes through the solution without scattering, indicating a true solution where the particles are two small to scatter light. In liquid 2, the light beam is visible because the particles are large enough to scatter the light, which is a characteristic of a colloid.
Question 22.
Two samples, ‘A’ and ‘B’, are taken for testing. Sample ‘A’ is a foam used in shaving cream, and sample ‘B’ is milk. Which of the following classifications is correct? (Competency-Based Question)
A. Sample ‘A’ is a solid sol and sample ‘B’ is an emulsion.
B. Sample ‘A’ is a foam (gas in liquid) and sample ‘B’ is a gel (liquid in solid).
C. Sample ‘A’ is a foam (gas in liquid) and sample ‘B’ is an emulsion (liquid in liquid).
D. Sample ‘A’ is an emulsion and sample ‘B’ is a sol (solid in liquid).
Answer:
(C) In foams like shaving cream, gas is dispersed in a liquid medium. Milk is an emulsion where liquid fat droplets are dispersed in water.
Question 23.
Study the given apparatus used for separating a mixture of ammonium chloride and common salt. Which of the following statements is correct?
A. Common salt changes directly into vapours and gets deposited on the funnel.
B. Ammonium chloride sublimes on heating and gets deposited on the cooler inner surface of the funnel.
C. Cotton plug is used to allow ammonium chloride vapours to escape easily.
D. This method is based on difference in solubility of the two solids.
Answer:
(B) Ammonium chloride is a sublimable solid, so on heating it changes directly into vapours and then solidifies on the cooler inner walls of the inverted funnel. Common salt does not sublime and remains in the china dish.
Question 24.
Match Column I with Column 11 and choose the correct option.
| Column I | Column II |
| 1. Brass | (i) Used in sculptures, coins, and bearings |
| 2. Bronze | (ii) Iron mixed with carbon, chromium, nickel, and molybdenum |
| 3. Stainless | (iii) Approximately 80% copper steel and 20% zinc |
| 4. Alloy | (iv) Homogeneous mixture of two or more metals, or a metal and a non-metal |
Codes
A. 1 – (iii), 2 – (i), 3 – (ii), 4 – (iv)
B. 1 – (i), 2 – (iii), 3 – (iv), 4 – (ii)
C. 1 – (ii), 2 – (iv), 3 – (i), 4 – (iii)
D. 1 – (iv), 2 – (ii), 3 – (iii), 4 – (i)
Answer:
(A) 1 – (iii), 2- (i), 3- (ii), 4 – (iv)
- Brass is approximately 80% copper and 20% zinc.
- Bronze is used in sculptures, coins, and bearings.
- Stainless steel is a mixture of iron with carbon, chromium, nickel, and molybdenum.
- An alloy is a homogeneous mixture of two or more metals or a metal and a non-metal.
Question 25.
Select the homogeneous mixture from the following.
A. Carbon dioxide gas dissolved in water.
B. Air containing suspended particles.
C. Soap bubbles formed by blowing air into soap solution.
D. Water in milk.
Answer:
A. Because both liquids are coloured
(A) Carbon dioxide gas dissolved in water (homogeneous mixture).
Question 26.
Which of the following substances shows Tyndall effect?
A. NaCl solution
B. Kerosene oil
C. Milk
D. Cold drink
Answer:
C. Milk
(C) Milk is a colloid which shows the Tyndall effect.
Question 27.
A student tries to separate mustard oil and water using distillation. Why is this not the best choice?
A. Because both liquids are coloured
B. Because they are immiscible and can be separated more easily by density difference
C. Because neither liquid can be heated
D. Because oil evaporates before water
Answer:
B. Because they are immiscible and can be separated more easily by density difference
(B) Mustard oil and water are immiscible and should be separated using a separating funnel based on their density difference rather than distillation.
Exploring Mixtures and Their Separation Class 9 Assertion and Reason Questions
Direction (Q.Nos. 1- 10): The following questions consist of two statements, Assertion (A) and Reason (R). Answer the questions by selecting the appropriate option given below.
A. Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
B. Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
C. Assertion is true, but Reason is false.
D. Assertion is false, but Reason is true.
Question 1.
Assertion (A): Solubility of a solids in liquids increases with temperature.
Reason (R): At higher temperatures, the kinetic energy of the particles increases.
Answer:
(A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion. Due to increased temperature, the particles of the solid and the liquid gain more kinetic energy, which helps the solid particles to break apart and dissolve faster in the liquid.
Question 2.
Assertion (A): Fractional distillation is used when the boiling points of two miscible liquids are very close.
Reason (R): Fractional distillation uses a fractionating column to allow repeated vaporisation and condensation.
Answer:
(A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion. The fractionating column allows repeated vaporisation and condensation, so it is used when the boiling points of two miscible liquids are very close.
Question 3.
Assertion (A): True solutions exhibit the Tyndall effect.
Reason (R): Particles are very small in size.
Answer:
(D) True solutions do not exhibit the Tyndall effect.
Since the particle size is very small in size. Hence, the Assertion is false, but Reason is true.
Question 4.
Assertion (A): The particles of a suspension can be seen with the naked eye.
Reason (R): Suspension is a homogeneous mixture.
Answer:
(C) Suspension is heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the liquid medium.
Thus, these particles can be seen with the naked eye. Hence, Assertion is true, but the reason is false.
Question 5.
Assertion (A): Colloidal particles do not show the Tyndall effect.
Reason (R): Colloidal solutions are stable, and colloidal particles do not settle down.
Answer:
(D) Colloidal particles scatter light, showing the Tyndall effect.
They are stable because the particles are very small and do not settle down on standing. Hence, Assertion is false, but Reason is true.
Question 6.
Assertion (A): Butter is classified as a gel, which is a type of colloid.
Reason (R): In butter, liquid fat is dispersed in solid components.
Answer:
(A) Butter is indeed a colloid classified as a gel.
The reason correctly states the structure of a gel, where a liquid (fat) is dispersed in a solid medium, which perfectly describes the composition of butter. Hence, both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
Question 7.
Assertion (A): Steel is an alloy.
Reason (R): Alloy are mixture of two or more metals or metal and a non-metal and cannot be separated into their components by physical
methods.
Answer:
(A) Steel is a homogeneous mixture (alloy) of iron and carbon.
In alloys, the constituent elements are combined in fixed proportions and cannot be separated by simple physical processes, though they retain metallic properties. Hence, both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
Question 8.
Assertion (A) A solution of table salt in a glass of water is homogeneous.
Reason (R) A solution having different composition throughout is homogeneous.
Answer:
(A) A salt solution is homogeneous because its composition and properties are uniform throughout.
Reason (R) is incorrect because a mixture with different compositions is defined as heterogeneous. not homogeneous. Thus, Assertion is true, but Reason is false.
Question 9.
Assertion (A): Tyndall effect is exhibited by a true solution.
Reason (R): Scattering of a beam of light by the colloidal particles is known as the Tyndall effect.
Answer:
(D) True solutions do not show a Tyndall effect.
Scattering of a beam of light by the colloidal particles is known as the Tyndall effect. Hence, the Assertion is false, but Reason is true.
Question 10.
Assertion (A): A suspension, such as chalk powder in water, is considered a heterogeneous mixture.
Reason (R): The particles in a suspension are large enough to be seen by the naked eye and settle down when left undisturbed.
Answer:
(A) A suspension is a heterogeneous mixture because the solute particles do not dissolve but remain suspended throughout the bulk of the medium.
These particles are visible to the naked eye and settle down when the mixture is left undisturbed, making the suspension unstable. Thus, both Assertion and Reason are true, and Reason is the correct explanation of Assertion.