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Chemistry Practice Questions

NCERT Class IX Chapter 2: Is Matter Around Us Pure?

Created & Curated By S.K. Sinha

Section A: Questions
Q1.
Which of the following statements are true for pure substances?
(i) Pure substances contain only one kind of particles
(ii) Pure substances may be compounds or mixtures
(iii) Pure substances have the same composition throughout
(iv) Pure substances can be exemplified by all elements and all compounds
(A) (i) and (ii)
(B) (i) and (iii)
(C) (i), (iii) and (iv)
(D) (ii), (iii) and (iv)
Q2.
Fractional distillation is used for separation of miscible liquids with a boiling point difference of:
(A) Less than 25K
(B) More than 25K
(C) Less than 273K
(D) More than 373K
Q3.
Which of the following are homogeneous mixtures?
(i) Ice (ii) Wood (iii) Air (iv) Soil
(A) (i) and (iii)
(B) (ii) and (iv)
(C) (i) and (ii)
(D) Only (iii)
Q4.
To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.
(A) 20%
(B) 25%
(C) 26.5%
(D) 36%
Q5.
Which separation techniques will you apply for the separation of the following?
(a) Sodium chloride from its solution in water
(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride
(c) Small pieces of metal in the engine oil of a car
(d) Different pigments from an extract of flower petals
(A) (a) Evaporation (b) Sublimation (c) Centrifugation (d) Chromatography
(B) (a) Filtration (b) Sublimation (c) Decantation (d) Evaporation
(C) (a) Sublimation (b) Evaporation (c) Filtration (d) Distillation
(D) (a) Distillation (b) Sublimation (c) Filtration (d) Chromatography
Q6.
Tincture of iodine has antiseptic properties. This solution is made by dissolving:
(A) Iodine in potassium iodide
(B) Iodine in vaseline
(C) Iodine in water
(D) Iodine in alcohol
Q7.
If we take a saturated solution of sodium chloride at 60ยฐC and cool it to room temperature, we get:
(A) An unsaturated solution
(B) A saturated solution
(C) A supersaturated solution
(D) A concentrated solution
Q8.
Which of the following is not a colloid?
(A) Smoke
(B) Milk
(C) Air
(D) Soap solution
Q9.
A mixture of sulphur and carbon disulphide is:
(A) Heterogeneous and shows Tyndall effect
(B) Homogeneous and shows Tyndall effect
(C) Heterogeneous and does not show Tyndall effect
(D) Homogeneous and does not show Tyndall effect
Q10.
Sea-water can be classified as a:
(A) Homogeneous mixture
(B) Heterogeneous mixture
(C) Compound
(D) Element
Q11.
Alloys are an example of:
(A) Solid in solid solution
(B) Solid in liquid solution
(C) Liquid in solid solution
(D) Gas in solid solution
Q12.
The Tyndall effect is observed only when following conditions are satisfied:
(a) The diameter of the dispersed particles is much smaller than the wavelength of the light used
(b) The diameter of the dispersed particles is not much smaller than the wavelength of the light used
(c) The refractive indices of the dispersed phase and dispersion medium are almost equal
(d) The refractive indices of the dispersed phase and dispersion medium differ greatly
(A) (a) and (c)
(B) (b) and (d)
(C) (a) and (d)
(D) (b) and (c)
Q13.
Which of the following will show "Tyndall effect"?
(A) Salt solution
(B) Milk
(C) Copper sulphate solution
(D) Sugar solution
Q14.
A colloidal solution of starch in water is:
(A) Hydrophobic sol
(B) Hydrophilic sol
(C) Intrinsic colloid
(D) Associated colloid
Q15.
Which of the following is a solution?
(A) Soil
(B) Sea water
(C) Coal
(D) Air with dust
Q16.
Mass percentage of a solution is 20% and the mass of the solution is 100g. The mass of the solute is:
(A) 20g
(B) 25g
(C) 40g
(D) 80g
Q17.
Which of the following mixtures would be easiest to separate?
(A) Sand and water
(B) Oil and water
(C) Salt and water
(D) Alcohol and water
Q18.
Solubility of a substance is affected by:
(A) Temperature of the solution
(B) Pressure
(C) Nature of solute and solvent
(D) All of the above
Q19.
A mixture of iron filings and sand can be separated by:
(A) Sublimation
(B) Magnetic separation
(C) Sieving
(D) Handpicking
Q20.
Which of the following is the best method for separation of naphthalene from a mixture of benzoic acid and naphthalene?
(A) Sublimation
(B) Crystallisation
(C) Distillation
(D) Fractional crystallisation
Q21.
Which of the following statements is/are true about solutions?
(i) A solution is a homogeneous mixture
(ii) Particle size of solute is less than 1 nm
(iii) Solutions are stable
(iv) Solute particles cannot be seen by naked eye
(A) (i), (ii) and (iii)
(B) (i), (ii) and (iv)
(C) (i), (iii) and (iv)
(D) All of the above
Q22.
Crystallisation technique is better than simple evaporation technique because:
(A) Crystals obtained are pure
(B) It gives better yield
(C) Impurities remain in the mother liquor
(D) All of the above
Q23.
CaCl2ยท6H2O on heating gives anhydrous CaCl2. The water of crystallisation is:
(A) 6 molecules
(B) 5 molecules
(C) 2 molecules
(D) 1 molecule
Q24.
Which of the following are physical changes?
(i) Melting of iron metal
(ii) Rusting of iron
(iii) Bending of an iron rod
(iv) Drawing a wire of iron metal
(A) (i), (ii) and (iii)
(B) (i), (iii) and (iv)
(C) (ii), (iii) and (iv)
(D) (ii) and (iv)
Q25.
The process of separation of different constituents of petroleum is:
(A) Crystallisation
(B) Fractional distillation
(C) Separating funnel
(D) Centrifugation
Section B: Answers
Question Answer
Q1 (C)
Q2 (A)
Q3 (D)
Q4 (C)
Q5 (A)
Q6 (D)
Q7 (C)
Q8 (C)
Q9 (D)
Q10 (A)
Q11 (A)
Q12 (B)
Q13 (B)
Q14 (B)
Q16 (A)
Q17 (B)
Q18 (D)
Q19 (B)
Q20 (A)
Q21 (D)
Q22 (D)
Q23 (A)
Q24 (B)
Q25 (B)
Section C: Solutions
Q1.
Pure substances contain only one kind of particles, have uniform composition, and include all elements and compounds.
Q2.
Fractional distillation separates liquids with boiling point differences less than 25K.
Q3.
Only air is homogeneous; ice is pure substance, wood and soil are heterogeneous mixtures.
Q4.
Concentration = (36/(36+100)) ร— 100 = 26.5%.
Q5.
NaCl: evaporation; NH4Cl: sublimation; metal pieces: centrifugation; pigments: chromatography.
Q6.
Tincture of iodine is iodine dissolved in alcohol (ethanol).
Q7.
Cooling decreases solubility; excess salt precipitates, making solution supersaturated.
Q8.
Air is a homogeneous mixture, not a colloid. Others show Tyndall effect.
Q9.
Sulphur dissolves in CS2 forming homogeneous solution; no Tyndall effect.
Q10.
Sea water is uniform mixture of water and dissolved salts (homogeneous).
Q11.
Alloys are solid metals dissolved in solid metals (solid-solid solution).
Q12.
Tyndall effect requires particle size comparable to light wavelength and different refractive indices.
Q13.
Milk is colloidal solution showing Tyndall effect; others are true solutions.
Q14.
Starch loves water (hydrophilic) forming stable colloidal solution.
Q15.
Sea water is homogeneous solution of salts in water.
Q16.
Mass of solute = 20% of 100g = 20g.
Q17.
Oil and water are immiscible; easily separated using separating funnel.
Q18.
Temperature, pressure, and nature of solute-solvent all affect solubility.
Q19.
Iron is magnetic; attracted by magnet, leaving sand behind.
Q20.
Naphthalene sublimes directly to vapor, separating from benzoic acid.
Q21.
All statements are true: homogeneous, particle size <1nm, stable, invisible particles.
Q22.
Crystallization gives pure crystals, better yield, and separates impurities effectively.
Q23.
Formula shows 6 water molecules attached to each CaCl2 unit.
Q24.
Melting, bending, and drawing wire are physical changes; rusting is chemical change.
Q25.
Petroleum components have different boiling points; separated by fractional distillation.

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