Exploring Mixtures and Their Separation Flashcards

Classification of Mixtures

• Definition of a Mixture: A material system formed by combining two or more physically distinct substances without chemical bonding.
• Homogeneous Mixtures (Solutions):
  • Definition: A mixture characterized by a uniform composition, appearance, and property profile throughout its bulk.
  • Properties: Solute particles dissolve completely down to the molecular or ionic scale. Samples taken from any portion of the mixture yield identical properties (e.g., a well-stirred solution of sugar in water exhibits identical sweetness from the top to the bottom sip).
  • Examples: Common salt ($NaCl$) dissolved in water, sugar dissolved in water, vinegar (acetic acid dissolved in water), aerated beverages like soda water (carbon dioxide gas dissolved in water under pressure), and metallic alloys like brass or bronze.
  • Permanence: A homogeneous mixture remains permanently uniform unless altered by external chemical or physical separation processes.
• Heterogeneous Mixtures:
  • Definition: A mixture that does not possess a uniform composition throughout.
  • Properties: Individual constituent particles remain physically distinct, often visible to the naked eye or under moderate magnification, and tend to separate or settle over time under gravity.
  • Examples: Sand mixed in water, chalk powder in water, mustard oil mixed in water, smoke (solid soot particles dispersed in air), fog (tiny liquid water droplets suspended in air), and muddy water.

Experimental Classification of Mixtures (Activity 5.1)

• Preparation of Experimental Groups:
  • Group A: Add $1$ spatula of common salt ($NaCl$) to $50\,mL$ of water in a transparent glass beaker; stir thoroughly. Label as Beaker A.
  • Group B: Add $1$ spatula of chalk powder to $50\,mL$ of water in a transparent glass beaker; stir thoroughly. Label as Beaker B.
  • Group C: Add a few drops of milk to $50\,mL$ of water in a transparent glass beaker; stir thoroughly. Label as Beaker C.
• Experimental Tests and Observations:
  1. Particle Visibility:
     • Beaker A: Solute particles are completely invisible.
     • Beaker B: Fine solid particles remain suspended and clearly visible throughout the liquid.
     • Beaker C: Liquid appears translucent/cloudy; individual particles are not distinct to the naked eye.
  2. Laser Light Scattering Test (Tyndall Test):
     • Direct a laser beam horizontally through each beaker and observe the path from the side at a $90^\circ$ angle perpendicular to the beam.
     • Safety Precaution: Direct eye contact with a laser beam must be strictly avoided as it causes irreversible retinal damage.
     • Beaker A: The laser beam path is invisible inside the solution.
     • Beaker B: The laser beam path is visible due to light scattering by large suspended chalk particles.
     • Beaker C: The laser beam path is visible due to light scattering by dispersed colloidal particles.
  3. Stability and Settling Test:
     • Allow the beakers to stand undisturbed for several minutes.
     • Beaker A: Solute remains evenly distributed; no settling occurs.
     • Beaker B: Suspended chalk particles settle to the bottom under gravity.
     • Beaker C: Colloidal particles remain dispersed; no settling occurs.
  4. Filtration Test:
     • Pass each mixture through standard filter paper mounted in a funnel.
     • Beaker A: Leaves no residue on the filter paper; filtrate remains clear.
     • Beaker B: Leaves a solid chalk residue on the filter paper; filtrate is clear water.
     • Beaker C: Leaves no residue on standard filter paper; milky filtrate passes through.

Solutions and Concentration

• Constituents of a Solution:
  • Solute: The component being dissolved, generally present in a smaller quantitative proportion.
  • Solvent: The dissolving medium, generally present in a larger quantitative proportion.
• Concept of Concentration:
  • Definition: Concentration is the quantitative measure of the amount of solute present in a specified mass or volume of solvent or total solution.
  • Importance of Precise Proportioning:
    • Oral Rehydration Solution (ORS): Prepared by dissolving precise, standardized amounts of salt and sugar in a fixed volume of water. Deviating from specified ratios yields a salt-sugar solution that is ineffective as clinical ORS. Developed by Indian pediatrician Dr. Dilip Mahalanabis to treat severe dehydration caused by diarrhea and cholera. Endorsed by the World Health Organization (WHO), saving millions of lives.
    • Agricultural Spraying: Pesticides must be mixed with water at exact recommended concentrations. Sub-optimal concentrations fail to eliminate pests, whereas excess concentrations cause crop injury, soil contamination, and environmental harm.
    • Medical Intravenous Fluids: Clinical saline drips utilize a precise $0.9\%\text{ m/v}$ sodium chloride ($NaCl$) solution in water ($0.9\,g$ $NaCl$ per $100\,mL$ solution), ensuring isotonic compatibility with human blood cells.
• Quantitative Formulations of Concentration:
  1. Mass by Mass Percentage ($\%\text{ m/m}$ or $\%\text{ w/w}$):         $\text{Mass by mass percentage} = \frac{\text{Mass of solute}}{\text{Mass of solution}} \times 100$$\text{Mass of solution} = \text{Mass of solute} + \text{Mass of solvent}$Applications: Common for solid-in-solid or solid-in-liquid mixtures, commercial powders (e.g., milk powder, spice mixtures), packaged food nutritional labeling (salt, sugar, protein content), and antiseptic talcum powders ($4\%\text{ m/m}$ zinc oxide). Weight by weight percentage ($\%\text{ w/w}$) is numerically identical to mass by mass percentage ($\%\text{ m/m}$).
  2. Mass by Volume Percentage ($\%\text{ m/v}$ or $\%\text{ w/v}$):         $\text{Mass by volume percentage} = \frac{\text{Mass of solute}}{\text{Volume of solution}} \times 100$Applications: Standard in clinical diagnostics, pharmacology, and liquid reagent preparations where volumetric measurement of liquid is more practical than mass measurement (e.g., $5\%\text{ m/v}$ glucose intravenous solution).
  3. Volume by Volume Percentage ($\%\text{ v/v}$):         $\text{Volume by volume percentage} = \frac{\text{Volume of solute}}{\text{Volume of solution}} \times 100$Applications: Used when mixing two or more miscible liquids, such as commercial vinegar ($5\%\text{ v/v}$ acetic acid in water), perfumes, cosmetics, and liquid pesticide concentrates.

Solubility Principles and Solubility Curves

• Definition of Solubility: The maximum mass of solute (in grams) capable of dissolving in a standard quantity of solvent ($100\,g$ or $100\,mL$ of water) at a specified temperature.
• Saturated Solution: A solution containing the maximum theoretical limit of dissolved solute at a specific temperature such that no further solute can dissolve upon stirring.
• Unsaturated Solution: A solution containing less solute than its saturation limit at a given temperature.
• Temperature Dependence of Solubility:
  • Solid Solutes in Liquid Solvents: Solubility generally increases as temperature rises.
  • Gaseous Solutes in Liquid Solvents: Solubility decreases as temperature rises.
• Solubility Curves (Activity 5.2 Analysis):
  • A solubility curve plots solute solubility ($g$ per $100\,g$ water on the y-axis) against temperature ($^\circ\text{C}$ on the x-axis).
  • Compound 'A' vs Compound 'B' Data:
    • Solubility of Compound 'B' at $40\,^\circ\text{C}$ is $241\,g$ per $100\,g$ water.
    • Solubility of Compound 'B' at $60\,^\circ\text{C}$ is $287\,g$ per $100\,g$ water.
    • Comparative trend: The solubility of Compound 'A' exhibits a significantly steeper rate of increase with rising temperature than Compound 'B'.

Methods for Separating Homogeneous Mixtures

• 1. Crystallization:

  • Definition: The separation process by which a dissolved solid is recovered in pure form as solid crystals from its saturated solution upon controlled cooling or evaporation.
  • Crystal Definition: A solid material whose constituent microscopic particles (atoms, ions, or molecules) are organized in a highly ordered, repeating three-dimensional geometric structure.
  • Natural Examples: Rock salt deposits, candy sugar crystals (mishri), snowflakes (frozen atmospheric water vapor), window frost, quartz mineral crystals, and natural cave formations (such as stalactites/stalagmites in Mawsmai Cave, Sohra/Cherrapunji).
  • Thermodynamic Principle: Relies on temperature-dependent solubility variations. Cooling a hot saturated solution forces solute out of solution because solubility drops below the dissolved mass concentration, precipitating pure solid crystals while leaving unwanted soluble impurities in the liquid mother liquor.
  • Laboratory Procedure (Copper Sulfate - Activity 5.3):
    1. Weigh $1\,g$ of copper sulfate ($CuSO_4$ / blue vitriol) into a $100\,mL$ beaker; add $25\,mL$ water and $1$ drop of dilute sulfuric acid ($H_2SO_4$) to prevent chemical hydrolysis.
    2. Heat the mixture gently in a water bath while stirring constantly. Add additional copper sulfate incrementally until no more dissolves and saturation is attained.
    3. Filter the hot saturated liquid through filter paper into a clean beaker to remove insoluble particulate contaminants.
    4. Cover the beaker with a watch glass and allow it to cool slowly at room temperature without mechanical vibration.
    5. Cooling Rate Effect: Slow undisturbed cooling allows extended time for ordered molecular packing, producing large, shiny, well-shaped blue crystals. Rapid cooling in ice-cold water forces rapid precipitation, resulting in small, poorly formed micro-crystals.
    6. Separate crystals by filtration, rinse with ice-cold water, and dry on a watch glass.
  • Historical/Industrial Salt Production: Ancient Indian methods include Panga salt (produced by boiling concentrated sea brines) and Karkatch salt (produced by solar evaporation of seawater in coastal salt pans).

• 2. Simple Distillation:

  • Definition: A process used to separate a liquid from a solution containing dissolved solids or to separate a mixture of two miscible liquids possessing a boiling point difference of at least $25\,^\circ\text{C}$.
  • Process Mechanism: The mixture is heated to the boiling point of the lower-boiling liquid component, driving it into the vapor phase. Vapors pass into a water-cooled condenser, where they transfer thermal energy, condense back into pure liquid (distillate), and drain into a separate collecting vessel. Higher-boiling components or solid solutes remain in the distillation flask.
  • Apparatus Components: Distillation flask, thermometer, heat source (burner, tripod, wire gauze), water condenser (with lower cooling water inlet and upper outlet), receiving conical flask, and laboratory supporting stands.
  • Separation of Acetone and Water: Acetone boils at approximately $56\,^\circ\text{C}$, whereas water boils at $100\,^\circ\text{C}$. The difference of $44\,^\circ\text{C}$ ($> 25\,^\circ\text{C}$) enables complete volatilization and condensation of pure acetone before water vaporizes significantly.
  • Traditional Perfumery Application: The traditional Deg-Bhapka distillation method in Kannauj, Uttar Pradesh ("Perfume Capital of India"), captures post-rain earthy soil aromas into natural perfume (Mitti ka Ittar). Facilities at the Fragrance and Flavour Development Centre in Kannauj support botanical extraction and commercial perfume manufacturing.

• 3. Fractional Distillation:

  • Definition: A physical separation technique employed to separate components of liquid mixtures whose boiling points differ by less than $25\,^\circ\text{C}$.
  • Process Mechanism: Utilizes a fractionating column packed with glass beads inserted between the distillation flask and condenser. The column provides a large surface area for repeated cycles of vapor condensation and re-vaporization, enabling precise separation of close-boiling fractions.
  • Industrial Application (Petroleum Refining): Crude petroleum extracted from the Earth's crust undergoes fractional distillation to separate components: Liquefied Petroleum Gas (LPG, compressed high-pressure steel cylinders used for domestic fuel), Petrol (gasoline), Aviation fuel/Kerosene, Diesel, Lubricating oil, Furnace oil, and Bitumen.

• 4. Paper Chromatography:

  • Etymology: Derived from the Greek words chroma ("color") and graphein ("to write").
  • Principle: Separates multi-component mixtures based on differential partitioning and differential migration rates between a stationary phase (filter paper/chromatography paper) and a mobile phase (eluting solvent).
  • Procedure (Activity 5.5):
    1. Cut a $3\,cm$ wide strip of chromatographic paper and draw a straight horizontal pencil line $2\,cm$ above the bottom edge.
    2. Deposit a small spot of black ink (or green food dye) at the center of the pencil line.
    3. Suspend the strip vertically inside a gas jar or beaker containing a thin bottom layer of water (or $2\%\text{ m/v}$ salt solution).
    4. Ensure the solvent liquid level is strictly below the applied sample spot.
    5. As solvent ascends through the paper by capillary action, solute components dissolve and travel upwards at different rates according to their relative solubility in the mobile solvent versus binding affinity to the paper fibers, resolving into distinct colored spots.

Methods for Separating Heterogeneous Mixtures

• 1. Separating Funnel (Immiscible Liquids):

  • Immiscible Liquids: Liquids that do not dissolve in one another and maintain distinct phase boundaries (e.g., mustard oil and water).
  • Principle: Operates on density differences. The denser liquid forms the lower layer, while the less dense liquid forms the upper layer.
  • Procedure (Activity 5.6):
    1. Pour a mixture of $5\,mL$ mustard oil and $20\,mL$ water into a $50\,mL$ separating funnel.
    2. Allow the funnel to stand undisturbed until two sharp layers form (denser water at the bottom, yellow mustard oil on top).
    3. Open the stopcock slowly to drain the lower water layer into a conical flask.
    4. Close the stopcock when the interface reaches the valve, discard the small interphase segment, and open the stopcock again to collect the pure upper oil layer in a separate container.
  • Gas Phase Note: Gases diffuse rapidly to form homogeneous gaseous mixtures (e.g., $H_2$ and $O_2$ rocket propellant). Heterogeneous gas mixtures occur when solid or liquid particles are suspended in air (e.g., smoke = solid carbon particles in air; fog = liquid water droplets in air).

• 2. Sublimation:

  • Sublimation: Direct phase transition of a substance from solid state to gaseous vapor state upon heating (below its melting point) without passing through an intermediate liquid phase.
  • Deposition: Direct phase transition of gaseous vapor back into pure solid state upon cooling without forming a liquid.
  • Procedure (Activity 5.7):
    1. Place a mixture of crushed camphor and sand inside a china dish supported on a tripod stand with wire gauze.
    2. Invert a glass funnel over the dish, plugging the top nozzle securely with a cotton ball.
    3. Heat the china dish gently with a burner. Camphor sublimes into gas, rises into the cooler funnel, and undergoes deposition into pure white solid camphor crystals along the inner glass wall. Non-sublimable sand remains in the china dish.
  • Sublimable Materials: Camphor, naphthalene, ammonium chloride ($NH_4Cl$), and solid carbon dioxide (dry ice, utilized in low-temperature refrigeration and ice cream storage).

• 3. Metallic Alloys:

  • Definition: A homogeneous solid mixture composed of two or more metals, or a metal and a non-metal, produced by fusing constituents in molten state at high temperatures and cooling.
  • Physical Separation Limits: Alloys cannot be separated into their constituent elements by physical separation techniques.
  • Examples and Exact Compositions:
    • Brass: Composition of approximately $80\%$ Copper ($Cu$) and $20\%$ Zinc ($Zn$).
    • Bronze: Composition of approximately $80\%$ Copper ($Cu$) and $20\%$ Tin ($Sn$).
    • Stainless Steel: Iron ($Fe$) alloyed with Carbon ($0.03 - 0.8\%$), Chromium ($16 - 18\%$), Nickel ($10.0 - 14.0\%$), and Molybdenum ($2.0 - 3.0\%$).

• 4. Suspensions and Separative Techniques:

  • Suspension Definition: A heterogeneous fluid mixture containing solid solute particles that do not dissolve, remaining suspended throughout the bulk liquid. Particle size exceeds $1000\,nm$ in diameter. Particles are visible to the naked eye and settle out under gravity when left undisturbed.
  • Centrifugation:
    • Mechanism: Rapid spinning of a liquid sample in high-speed rotational equipment. Generated centrifugal force (outward force during circular movement) drives denser suspended solid particles outward to the bottom of the centrifuge tube (pellet), leaving the lighter liquid supernatant above.
    • Clinical/Industrial Use: Separation of whole blood into red blood cells, white blood cells/platelets, and liquid plasma.
    • Paperfuge Technology: A manual, unpowered centrifuge constructed from a cardboard disc, tape, string, and handles (inspired by traditional spinning games like phugadi in Marathi or kikli in Punjabi). Reaches extreme rotational speeds without electricity to isolate blood components for field diagnosis of malaria and anemia in low-resource locations.
  • Coagulation and Flocculation:
    • Mechanism: Addition of a chemical coagulant (such as powdered alum / fitkari) to turbid/muddy water. The coagulant neutralizes particle charges, causing fine suspended micro-particles to aggregate into larger clumps (flocs).
    • Sedimentation & Decantation: These larger clumps settle rapidly by gravity (sedimentation) to the container bottom, enabling clear liquid separation via decantation or filtration.
    • Dairy Coagulation: Production of cottage cheese (paneer) from milk by adding organic acids (lemon juice or vinegar) as coagulants to precipitate milk proteins.

Colloids, Emulsions, and the Tyndall Effect

• Colloid Definition: A heterogeneous system in which intermediate-sized particles ($1\,nm$ to $1000\,nm$ in diameter) are uniformly dispersed throughout a continuous medium. Particles do not settle upon standing and pass through standard filter paper.
• Structural Components of Colloids:
  • Dispersed Phase: The discontinuous phase comprising colloidal particles (analogous to solute).
  • Dispersion Medium: The continuous phase in which colloidal particles are suspended (analogous to solvent).
• Emulsions:
  • Colloidal systems where both the dispersed phase and the dispersion medium are liquids.
  • Oil-in-Water (O/W) Emulsions: Oil droplets dispersed throughout water (e.g., milk, vanishing creams).
  • Water-in-Oil (W/O) Emulsions: Water droplets dispersed throughout oil (e.g., butter, cold creams, body lotions).
  • Emulsifying Agents: Surface-active substances (e.g., milk proteins) that stabilize emulsions and prevent phase separation.
• Tyndall Effect:
  • Definition: The scattering of a light beam as it passes through a colloidal dispersion or suspension, rendering the light path visible from the side.
  • Mechanism: Dispersed particles ($1\,nm - 1000\,nm$) possess dimensions comparable to visible light wavelengths, scattering incident light rays. Solutions do not exhibit the Tyndall effect because solute particles ($< 1\,nm$) are too small to scatter visible light.
  • Real-World Manifestations: Sunlight filtering through small gaps in dense forest canopy foliage; a sunlight beam penetrating a dark room via a pinhole (scattered by airborne soot and dust particles); floodlight beams in sports stadiums; and atmospheric optical haze in urban polluted air.

Comparative Matrix of Mixture Types

Real-World Applications, Ethics, and Environmental Implications

• Physiological Filtration: Human kidneys continuously filter metabolic nitrogenous wastes from blood plasma.
• Environmental Remediation: Cleanup of marine plastic contaminants; municipal sewage treatment processing including sequential sedimentation, coagulation, and filtration stages to yield recycled non-potable water for irrigation and toilet flushing.
• Resource Recycling: Domestic waste segregation into dry recyclable fractions (paper, glass, metals, plastics) versus wet compostable organics; industrial extraction of valuable lithium metal from discarded lithium-ion batteries.
• Medical Blood Donation: Donated blood undergoes centrifugation to isolate specific fractions (plasma, platelets, white blood cells, and red blood cells) stored in blood banks for blood transfusions. The human body naturally regenerates donated volume within a few weeks.

Complete Solved Examples and Numerical Exercises

Text Examples

• Example 5.1: Calculate the mass by mass percentage of a solution formed by dissolving $10\,g$ of common salt in $90\,g$ of water.
  • Mass of solute ($NaCl$) = $10\,g$
  • Mass of solvent (water) = $90\,g$
  • Total mass of solution = $10\,g + 90\,g = 100\,g$
  • $\text{Mass by mass percentage} = \frac{10\,g}{100\,g} \times 100 = 10\%\text{ m/m}$
• Example 5.2: Calculate the mass by volume percentage of a solution formed by dissolving $5\,g$ of glucose in water to make $100\,mL$ of total solution.
  • Mass of solute (glucose) = $5\,g$
  • Volume of solution = $100\,mL$
  • $\text{Mass by volume percentage} = \frac{5\,g}{100\,mL} \times 100 = 5\%\text{ m/v}$
• Example 5.3: Calculate the volume by volume percentage of a pesticide spray formed by mixing $1\,mL$ of liquid pesticide with sufficient water to yield $100\,mL$ of spray solution.
  • Volume of solute (pesticide) = $1\,mL$
  • Total volume of solution = $100\,mL$
  • $\text{Volume by volume percentage} = \frac{1\,mL}{100\,mL} \times 100 = 1\%\text{ v/v}$

Pause and Ponder Problems

1. Zinc Oxide in Talcum Powder: Antiseptic talcum powder contains $4\%\text{ m/m}$ zinc oxide. Calculate the mass of zinc oxide in $300\,g$ of powder.
   • $\text{Mass of Zinc Oxide} = \frac{4}{100} \times 300\,g = 12\,g$
2. Orange Juice Concentration: Mixing $2$ tablespoons ($15\,mL$ each) of concentrate to yield $150\,mL$ of final juice per person. Calculate $\%\text{ v/v}$.
   • Solute volume = $2 \times 15\,mL = 30\,mL$
   • Total solution volume = $150\,mL$
   • $\text{Volume by volume percentage} = \frac{30\,mL}{150\,mL} \times 100 = 20\%\text{ v/v}$
3. Vinegar Preparation from Glacial Acetic Acid: Commercial vinegar is $5\%\text{ v/v}$ acetic acid. Glacial acetic acid is $100\%$ liquid acetic acid.
   • Procedure: Measure $5\,mL$ of pure glacial acetic acid and add distilled water while stirring until the total volume reaches exactly $100\,mL$
4. Cooling Saturated Solutions A and B: Referring to Activity 5.2 solubility curves, equal masses of hot saturated solutions of 'A' and 'B' are cooled from $80\,^\circ\text{C}$ to $60\,^\circ\text{C}$.
   • Outcome: Solution 'A' deposits more solid mass because the curve slope for 'A' drops much more steeply between $80\,^\circ\text{C}$ and $60\,^\circ\text{C}$ than for 'B'.
5. Evaporation Rate and Salt Crystal Size: Increasing the evaporation rate reduces crystal size (yielding small micro-crystals), whereas decreasing the evaporation rate allows extended growth time, forming larger, well-defined crystals.

Revise, Reflect, Refine Exercises

1. Correct Mixture Classification:
   • Correct Option: (iv) Muddy water — Ht, Milk — Ht, Blood — Ht, Brass — Hm.
2. Tyndall Effect Selection:
   • Correct Option: (iii) a and c (Air + dust particles; Starch + water).
   • Reason: Dust in air (heterogeneous suspension) and starch in water (colloid) possess particle sizes within $1-1000\,nm$ or greater, scattering light. Copper sulfate in water and acetone in water form true solutions ($< 1\,nm$), which cannot scatter light.
3. Categorization Matrix:
   • Solution: Small-sized particles ($< 1\,nm$); Particles remain evenly distributed; Does not settle down; Cannot be separated by filtration; Transparent. Examples: Salt solution, Brass.
   • Suspension: Large-sized particles ($> 1000\,nm$); Settles down when left undisturbed; Separates by filtration; Heterogeneous mixture. Examples: Sand in water, Mud, Chalk powder.
   • Colloid: Moderate-sized particles ($1 - 1000\,nm$); Scatters light; Does not settle down; Cannot be separated by filtration; Heterogeneous mixture. Examples: Milk, Butter, Smoke.
4. Mathematical Calculations:
   • (i) Cake Recipe Component Percentages:
     • Mass of sugar = $75\,g$
     • Mass of flour = $420\,g$
     • Mass of sodium hydrogencarbonate = $5\,g$
     • Total dry mixture mass = $75\,g + 420\,g + 5\,g = 500\,g$
     • $\text{Concentration of Sugar} = \frac{75\,g}{500\,g} \times 100 = 15\%\text{ m/m}$
     • $\text{Concentration of Flour} = \frac{420\,g}{500\,g} \times 100 = 84\%\text{ m/m}$
     • $\text{Concentration of Sodium Hydrogencarbonate} = \frac{5\,g}{500\,g} \times 100 = 1\%\text{ m/m}$
   • (ii) Brass Alloy Masses:
     • Total mass of brass = $120\,g$
     • $\text{Mass of Copper} = 70\% \times 120\,g = 84\,g$
     • $\text{Mass of Zinc} = 120\,g - 84\,g = 36\,g$
5. Cooking Oil and Water Separation:
   • Oil mass = $910\,g$ per $1000\,mL$ (density = $0.91\,g/mL$). Water density = $1.0\,g/mL$.
   • Behavior: Oil is immiscible and forms a distinct upper layer because it is less dense than water.
   • Separation: Separate using a separating funnel; drain lower water layer through the stopcock, then collect the upper oil layer separately.
6. Assertion and Reason (Tyndall Effect in Solutions):
   • Assertion (A): Solutions do not exhibit the Tyndall effect. (True)
   • Reason (R): The particles in solutions are larger than 100 nm. (False; solute particles are less than $1\,nm$).
   • Correct Option: (iii) A is true, but R is false.
7. Separation Methods Table:

8. Separation of Miscible Liquids A ($60\,^\circ\text{C}$) and B ($90\,^\circ\text{C}$):
   • Method: Simple Distillation.
   • Reason: Boiling point difference is $90\,^\circ\text{C} - 60\,^\circ\text{C} = 30\,^\circ\text{C}$, which exceeds the required $25\,^\circ\text{C}$ threshold.
9. Comparison of Evaporation, Crystallization, and Distillation:
   • Evaporation: Used to recover a non-volatile solid solute from a solution when the solvent is not needed.
   • Crystallization: Preferred when pure solid crystals of high chemical purity are required without thermal decomposition.
   • Distillation: Preferred when the liquid solvent must be recovered or when two miscible liquids with distinct boiling points must be separated.
10. Blood Colloidal System Analysis:
    • (i) If blood behaved as a true suspension: Blood cells would settle out under gravity inside blood vessels during rest, blocking circulatory flow.
    • (ii) Dispersed phase and medium: Dispersed phase consists of cellular elements (red blood cells, white blood cells, platelets); Dispersion medium is liquid blood plasma.
11. Sequential Separation of Sand, Common Salt, and Naphthalene:
    • Step 1: Heat the dry solid mixture in a china dish covered with an inverted funnel to sublime and collect Naphthalene on the cool inner glass walls.
    • Step 2: Add water to the remaining sand-salt residue to dissolve common salt ($NaCl$); filter the mixture to recover Sand as the filter paper residue.
    • Step 3: Evaporate or crystallize the remaining filtrate liquid to recover pure Common Salt.
12. Efficacy of Water-Acetone Distillation:
    • Acetone boils at $56\,^\circ\text{C}$ and water boils at $100\,^\circ\text{C}$. The boiling point difference of $44\,^\circ\text{C}$ ($> 25\,^\circ\text{C}$) allows acetone to vaporize completely while water remains liquid in the distillation flask.
13. Solubility Data Table Analysis:

*   *(i) Mass of $KNO_3$ for saturated solution in $50\,g$ water at 40 °C*:
    *   Solubility at $40\,^\circ\text{C} = 62\,g$ per $100\,g$ water.
    *   For $50\,g$ water: $\text{Mass required} = \frac{62}{2} = 31\,g$
*   *(ii) Cooling saturated $KCl$ solution from 80 °C to 25 °C*:
    *   Solubility at $80\,^\circ\text{C} = 54\,g$ per $100\,g$ water; solubility at $25\,^\circ\text{C} \approx 36.2\,g$ per $100\,g$ water.
    *   *Observation*: Solid $KCl$ crystals precipitate out of solution because solubility decreases upon cooling.
*   *(iii) Comparative solubility variations from 10 °C to 80 °C*:
    *   $KNO_3$ solubility increases drastically (by $146\,g$).
    *   $NH_4Cl$ solubility increases significantly (by $42\,g$).
    *   $KCl$ solubility increases moderately (by $19\,g$).
    *   $NaCl$ solubility remains nearly constant (increases by only $1\,g$).

14. Three Student Solutions Comparison:
    • Student A: $20\,g$ sugar in $80\,g$ water. Total = $100\,g$. Concentration = $\frac{20}{100} \times 100 = 20\%\text{ m/m}$.
    • Student B: $20\,g$ sugar in $100\,g$ water. Total = $120\,g$. Concentration = $\frac{20}{120} \times 100 = 16.67\%\text{ m/m}$.
    • Student C: $30\,g$ sugar in $80\,g$ water. Total = $110\,g$. Concentration = $\frac{30}{110} \times 100 = 27.27\%\text{ m/m}$.
    • Conclusion: Student C's solution is the most concentrated ($27.27\%\text{ m/m}$) because it has the highest ratio of solute mass to total solution mass.
15. Distillation Technique Analysis (Boiling Point Data Table):

*   *(i) Separation Technique S*: Fractional Distillation (or Simple Distillation depending on boiling point delta).
*   *(ii) Apparatus Labels*: A = Distillation Flask, B = Water Condenser, C = Receiving Conical Flask.
*   *(iii) Separable Mixtures by Simple Distillation ($\Delta T \ge 25\,^\circ\text{C}$)*:
    *   (a) Water ($100\,^\circ\text{C}$) — Acetone ($56\,^\circ\text{C}$): $\Delta T = 44\,^\circ\text{C}$ (Simple Distillation).
    *   (b) Water ($100\,^\circ\text{C}$) — Salt: Liquid-solid mixture (Simple Distillation).
*   *(iv) Separable Mixtures by Fractional Distillation ($\Delta T < 25\,^\circ\text{C}$)*:
    *   (c) Acetone ($56\,^\circ\text{C}$) — Alcohol ($78\,^\circ\text{C}$): $\Delta T = 22\,^\circ\text{C}$.
    *   (e) Alcohol ($78\,^\circ\text{C}$) — Chloroform ($61\,^\circ\text{C}$): $\Delta T = 17\,^\circ\text{C}$.
    *   (f) Alcohol ($78\,^\circ\text{C}$) — Benzene ($80\,^\circ\text{C}$): $\Delta T = 2\,^\circ\text{C}$.