CBSE Class 9 Science Chapter 05 Exploring Mixtures And Their Separation MCQs Set 03

Multiple Choice Questions (MCQs) for Class 9 Science: Chapter 05 Exploring Mixtures And Their Separation

Review structured MCQ sets for Class 9 Science Chapter 05 Exploring Mixtures And Their Separation. Built according to official CBSE guidelines, these downloadable questions support daily revision and core concept reinforcement.

Practice Chapter 05 Exploring Mixtures And Their Separation MCQs for Class 9 Science

Access the complete set of multiple-choice questions for Chapter 05 Exploring Mixtures And Their Separation below. This focused format allows students to isolate specific topics for thorough review and uninterrupted practice alongside official CBSE textbooks.

Question: In Activity 5.1, laser light was shone through three beakers containing salt water, chalk-powder water and milk. Going by the Tyndall effect described later in the chapter, in which of these would the light beam most likely remain visible from the side?
A. Only the salt-water mixture
B. The chalk-powder mixture and the milk mixture
C. None of the three mixtures
D. All three mixtures equally
Show Answer & Explanation

Answer: (B) The chalk-powder mixture and the milk mixture

Explanation:
Salt dissolves to form a true solution, so its particles are too small to scatter light and the beam passes through unseen. Chalk powder in water is a suspension and milk is a colloid, both of which contain particles large enough to scatter light, making the beam's path visible.

Question: As this chapter uses the term, what does 'concentration' of a solution actually mean?
A. The colour intensity of the solution
B. The amount of solute present in a given amount of solvent or solution
C. The exact temperature at which a solute dissolves completely
D. The total volume of solvent required to prepare any solution
Show Answer & Explanation

Answer: (B) The amount of solute present in a given amount of solvent or solution

Explanation:
Concentration simply tells us how much solute is packed into a fixed amount of solvent or solution, which is why getting proportions right matters so much when preparing things like ORS or pesticide sprays.

Question: If 8 g of common salt is stirred into 72 g of water until it dissolves completely, what is the mass by mass percentage of the solution formed?
A. 8% m/m
B. 10% m/m
C. 11% m/m
D. 20% m/m
Show Answer & Explanation

Answer: (B) 10% m/m

Explanation:
Total mass of solution = 8 g + 72 g = 80 g. Applying the formula, mass by mass percentage = (8/80) x 100 = 10% m/m.

Question: A pharmacist dissolves 10 g of a medicinal salt in water to prepare 250 mL of an injectable solution. What is its concentration expressed as mass by volume percentage?
A. 2.5% m/v
B. 4% m/v
C. 10% m/v
D. 25% m/v
Show Answer & Explanation

Answer: (B) 4% m/v

Explanation:
Mass by volume percentage = (mass of solute / volume of solution) x 100 = (10 g / 250 mL) x 100 = 4% m/v.

Question: Based on the chapter's discussion of solubility, what generally happens to the solubility of a gas dissolved in a liquid as the liquid's temperature is raised?
A. It increases steadily
B. It generally decreases
C. It stays completely unchanged
D. It first increases and then decreases sharply
Show Answer & Explanation

Answer: (B) It generally decreases

Explanation:
Unlike solids, whose solubility in liquids usually rises with temperature, dissolved gases behave the opposite way and tend to escape more easily as the liquid gets warmer, lowering their solubility.

Question: How does the chapter define a saturated solution?
A. A solution in which the solute and solvent are present in exactly equal masses
B. A solution that has already been filtered to remove all impurities
C. A solution that cannot dissolve any additional solute at that particular temperature
D. A solution in which the solute has completely settled at the bottom
Show Answer & Explanation

Answer: (C) A solution that cannot dissolve any additional solute at that particular temperature

Explanation:
Once a solution reaches its solubility limit at a given temperature, no more solute will dissolve into it no matter how much is added or stirred; that state is what defines saturation.

Question: The chapter describes cooling a saturated solution of compound B from 60 °C to 40 °C, where its solubility falls from 287 g to 241 g per 100 g of water. For 100 g of water used, how much of compound B would separate out as solid during this cooling?
A. 241 g
B. 46 g
C. 287 g
D. 528 g
Show Answer & Explanation

Answer: (B) 46 g

Explanation:
Only 241 g of B can stay dissolved at 40 °C, so the excess beyond that amount comes out of solution as crystals: 287 g - 241 g = 46 g.

Question: According to the chapter, simple distillation works well for separating two miscible liquids only when their boiling points differ by roughly how much?
A. 5 degrees Celsius
B. 15 degrees Celsius
C. 25 degrees Celsius
D. 50 degrees Celsius
Show Answer & Explanation

Answer: (C) 25 degrees Celsius

Explanation:
A gap of at least about 25 degrees Celsius ensures one liquid vaporises well before the other, allowing clean separation; smaller gaps call for fractional distillation instead.

Question: What exactly is 'Mitti ka Ittar', as described in the chapter's account of Kannauj's traditional perfume-making?
A. A synthetic perfume manufactured only in modern factories using fragrant flowers
B. A natural perfume that captures the earthy fragrance released after the first rain, prepared through a traditional distillation method
C. A type of soap made through the coagulation of milk proteins
D. A metal alloy used to make traditional perfume containers
Show Answer & Explanation

Answer: (B) A natural perfume that captures the earthy fragrance released after the first rain, prepared through a traditional distillation method

Explanation:
• The fragrance rising from wet earth after rain is captured and distilled
• It is turned into a perfume through the traditional Deg-Bhapka method
• This craft has been practised across generations in Kannauj, the town called India's perfume capital

Question: During the fractional distillation of crude petroleum, which fraction is compressed into steel cylinders for use as a domestic cooking fuel?
A. Bitumen
B. Lubricating oil
C. Petroleum gas (LPG)
D. Diesel
Show Answer & Explanation

Answer: (C) Petroleum gas (LPG)

Explanation:
The gaseous fraction obtained at the top of the fractionating column is liquefied under pressure and supplied as Liquefied Petroleum Gas, commonly used for cooking at home.

Question: The word 'chromatography' comes from Greek roots that literally mean:
A. To separate liquids
B. Writing with colour
C. Measuring purity of a mixture
D. Mixing substances together
Show Answer & Explanation

Answer: (B) Writing with colour

Explanation:
Chroma means colour and graphein means to write, reflecting how the technique was originally developed to study coloured substances such as dyes and inks.

Question: Which of the following pairs is cited in the chapter as an example of substances that do not mix, forming a heterogeneous mixture?
A. Iron filings and sulfur
B. Sugar and water
C. Acetic acid and water
D. Carbon dioxide and water
Show Answer & Explanation

Answer: (A) Iron filings and sulfur

Explanation:
The chapter lists iron filings mixed with sulfur, alongside sand and water, as examples where the components stay physically distinct rather than blending uniformly.

Question: What visual feature mainly helps distinguish a suspension from a colloid, as explained in the chapter?
A. Suspension particles are visible to the naked eye and settle over time, while colloidal particles stay dispersed
B. Colloids always appear coloured while suspensions are always colourless
C. Suspensions dissolve fully over time while colloids never do
D. Colloids can always be separated easily by ordinary filtration but suspensions cannot
Show Answer & Explanation

Answer: (A) Suspension particles are visible to the naked eye and settle over time, while colloidal particles stay dispersed

Explanation:
Because suspension particles are larger than 1000 nm, they can be seen without any instrument and gradually settle under gravity; colloidal particles are smaller and remain evenly spread throughout the mixture instead.

Question: In colloids like milk and butter, what role do the proteins present in them play, according to the chapter?
A. They act as coagulants that cause the mixture to clump
B. They act as emulsifying agents that keep the emulsion stable
C. They cause fat droplets to sink and settle at the bottom
D. They intensify the scattering of light passing through the mixture
Show Answer & Explanation

Answer: (B) They act as emulsifying agents that keep the emulsion stable

Explanation:
Proteins in milk and butter stabilise the emulsion by preventing the dispersed oil droplets and the water-based medium from separating out, which is why these emulsifying agents are essential to such colloids.

Question: Bronze, as mentioned in the chapter, is roughly 80% copper and 20% tin by mass. How much copper would be present in a 50 g sample of bronze?
A. 10 g
B. 20 g
C. 40 g
D. 45 g
Show Answer & Explanation

Answer: (C) 40 g

Explanation:
80% of 50 g works out to 40 g, meaning the remaining 10 g would be tin.

Question: According to the chapter's note on traditional salt-making, how did coastal communities in India obtain panga salt?
A. By boiling concentrated sea brine
B. By evaporating seawater slowly in open pans
C. By filtering seawater through cloth repeatedly
D. By freezing seawater and collecting the ice
Show Answer & Explanation

Answer: (A) By boiling concentrated sea brine

Explanation:
The chapter distinguishes two traditional methods used along India's coasts: panga salt came from boiling down concentrated brines, while karkatch salt was produced simply by letting seawater evaporate.

Question: The Mawsmai Cave in Sohra (Cherrapunji) is mentioned in the chapter as an example of what?
A. A site of naturally occurring crystal formations
B. A location where fractional distillation was first practised
C. A natural source of camphor used in sublimation
D. A place known for alum mining
Show Answer & Explanation

Answer: (A) A site of naturally occurring crystal formations

Explanation:
It appears alongside quartz as an example showing that crystals are not only made in labs but also form naturally in places like caves and within the Earth's crust.

Question: Why does the chapter classify a mixture of hydrogen and oxygen gases, used as rocket fuel, as a homogeneous mixture?
A. Gas particles move freely in all directions, allowing them to mix uniformly
B. Hydrogen and oxygen always react to form a single compound
C. The two gases have identical densities
D. Gases can never be separated once combined
Show Answer & Explanation

Answer: (A) Gas particles move freely in all directions, allowing them to mix uniformly

Explanation:
Because gas particles are not confined to fixed positions, they spread out and blend evenly with other gases, which is why the chapter states that most gas-gas mixtures turn out homogeneous rather than heterogeneous.

Question: Apart from separating two miscible liquids, what other kind of separation does the chapter say distillation can achieve?
A. Obtaining a liquid from a solution that has a dissolved solid in it
B. Separating two immiscible liquids of different densities
C. Separating two solids that both sublime
D. Splitting a gaseous mixture into its pure components
Show Answer & Explanation

Answer: (A) Obtaining a liquid from a solution that has a dissolved solid in it

Explanation:
The text notes that distillation is not limited to liquid-liquid mixtures; it can also recover the pure liquid solvent from a solution where a solid has been dissolved in it.

Question: In Activity 5.3, why is a drop of dilute sulfuric acid added while preparing the copper sulfate solution for crystallization?
A. It prevents unwanted reactions and helps larger, pure crystals to form
B. It speeds up the evaporation of water from the beaker
C. It raises the melting point of copper sulfate
D. It gives the crystals their blue colour
Show Answer & Explanation

Answer: (A) It prevents unwanted reactions and helps larger, pure crystals to form

Explanation:
The blue colour of copper sulfate crystals comes from the compound itself, not the acid.
Sulfuric acid's actual job here is to stop side reactions during heating so that the crystals that eventually form are cleaner and more well-defined.
The chapter also notes this acid step is needed only for some salts, not all crystallization processes.

Question: A hospital saline drip is labelled 0.9% m/v sodium chloride. What does this figure actually represent?
A. 0.9 g of salt dissolved in every 100 mL of the solution
B. 0.9 mL of salt solution added to every 100 g of water
C. 0.9 g of salt present in every 100 g of solvent used
D. 0.9 percent of the drip bottle is filled with air
Show Answer & Explanation

Answer: (A) 0.9 g of salt dissolved in every 100 mL of the solution

Explanation:
Mass by volume percentage always reports grams of solute per 100 millilitres of total solution, so a 0.9% m/v label directly means 0.9 g of salt is present in each 100 mL of the saline drip.

Question: While trying paper chromatography on pigments from spinach leaves or flower petals, why might plain water fail to give good separation?
A. Some pigments dissolve better in a solvent like alcohol than in water
B. Water reacts chemically with the coloured pigments
C. Water evaporates too fast for the paper to absorb it
D. Chromatographic paper cannot absorb water at all
Show Answer & Explanation

Answer: (A) Some pigments dissolve better in a solvent like alcohol than in water

Explanation:
The chapter points out that although water works fine for ink on paper, extracting and separating plant pigments sometimes calls for alcohol or a mixture of solvents instead, since not every pigment moves well through paper when carried by water alone.

Question: Which method would correctly separate a mixture of naphthalene and sand?
A. Sublimation, since naphthalene turns directly into vapour while sand stays behind
B. Filtration, since sand dissolves in water while naphthalene does not
C. Magnetic separation, since sand responds to a magnet
D. Distillation, since the two substances share a similar boiling point
Show Answer & Explanation

Answer: (A) Sublimation, since naphthalene turns directly into vapour while sand stays behind

Explanation:
Naphthalene behaves like camphor in the chapter's sublimation activity — it passes straight from solid to vapour on gentle heating, leaving the non-sublimable sand behind to be collected separately.

Question: Unlike sand particles in muddy water, the dispersed particles of a colloid such as milk stay evenly spread through the liquid indefinitely. What best explains this difference?
A. Colloidal particles are much smaller than suspension particles, so gravity does not pull them down noticeably
B. Milk is chemically bonded to water at a molecular level
C. Colloidal mixtures are constantly stirred by hand to prevent settling
D. Colloids contain no solid matter at all
Show Answer & Explanation

Answer: (A) Colloidal particles are much smaller than suspension particles, so gravity does not pull them down noticeably

Explanation:
The chapter places colloid particles in the 1-1000 nm range, far smaller than the greater-than-1000 nm particles found in suspensions like muddy water. This size difference is why colloids stay uniformly dispersed while suspensions settle over time.

Question: The chapter lists which pair of substances as an example of two things that simply do not mix, much like oil and water?
A. Iron filings and sulfur
B. Sugar and water
C. Vinegar and water
D. Carbon dioxide and water
Show Answer & Explanation

Answer: (A) Iron filings and sulfur

Explanation:
Right after describing oil and water forming separate layers, the text adds iron filings and sulfur as another everyday pair that stays unmixed, both being cited as examples of heterogeneous mixtures.

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