A non-volatile solute is added to a solvent. The vapor pressure of the solution
A increases
B decreases
C remains same
D becomes zero
Addition of non-volatile solute reduces mole fraction of solvent, lowering vapor pressure.
Relative lowering of vapor pressure is independent of
A mole fraction of solute
B nature of solute
C number of solute particles
D concentration of solution
It is a colligative property depending only on number of particles.
If vapor pressure of pure solvent is 120 mmHg and solution vapor pressure is 108 mmHg, relative lowering is
A 0.05
B 0.10
C 0.15
D 0.20
(120 − 108)/120 = 12/120 = 0.10.
Mole fraction of solute in the above solution is
A 0.05
B 0.10
C 0.90
D 0.12
Relative lowering of vapor pressure equals mole fraction of solute.
Raoult’s law applies best when
A solute is volatile
B solution is dilute and ideal
C solute is electrolyte
D solution shows strong interactions
Ideal behavior is best approximated in dilute solutions.
Which pair forms an ideal solution
A ethanol + water
B acetone + chloroform
C benzene + toluene
D HCl + water
Similar molecular size and intermolecular forces → ideal behavior.
In negative deviation from Raoult’s law, vapor pressure of solution is
A higher than ideal
B lower than ideal
C equal to ideal
D zero
Strong A–B interactions reduce escaping tendency of molecules.
Solutions showing negative deviation form
A minimum boiling azeotrope
B maximum boiling azeotrope
C no azeotrope
D minimum freezing azeotrope
Lower vapor pressure → higher boiling point.
Azeotropes are mixtures which
A have constant boiling point
B have constant freezing point
C show no vapor pressure
D contain solids only
Liquid and vapor have same composition at azeotrope.
Azeotropes cannot be separated by
A crystallization
B filtration
C simple distillation
D adsorption
Vapor composition equals liquid composition.
Freezing point of a solvent is lowered by 0.186 K for a 0.1 m solution. Kf of solvent is
A 0.93
B 1.86
C 18.6
D 0.186
ΔTf = Kf m → Kf = 0.186 / 0.1 = 1.86.
Boiling point elevation increases when
A solvent molar mass increases
B solute molar mass increases
C solute concentration increases
D temperature decreases
ΔTb ∝ molality.
Which colligative property is least affected by temperature
A vapor pressure lowering
B osmotic pressure
C boiling point elevation
D freezing point depression
It is directly related to mole fraction.
A solution has higher boiling point because
A vapor pressure is lower
B vapor pressure is higher
C surface tension increases
D solute evaporates
More heat is required to make vapor pressure equal atmospheric pressure.
Osmotic pressure of solution depends on
A molality
B molarity
C mole fraction
D density
π = MRT → depends on molarity.
If osmotic pressure of solution is doubled, molarity becomes
A half
B same
C double
D four times
π ∝ M.
Van’t Hoff factor for CaCl₂ in dilute aqueous solution is approximately
A 1
B 2
C 3
D 4
CaCl₂ → Ca²⁺ + 2Cl⁻ (3 particles).
Van’t Hoff factor becomes less than theoretical value due to
A dissociation
B hydration
C ion pairing
D dilution
Ion pairing reduces effective number of particles.
If van’t Hoff factor is 0.5, solute undergoes
A dissociation
B association
C ionization
D hydrolysis
Association reduces number of particles.
Colligative properties are useful for determining
A density of solute
B color of solute
C molar mass of solute
D boiling point of solvent
They depend on number of particles, allowing molar mass calculation.
Adsorption of gases on solids increases with
A increase in temperature
B decrease in pressure
C increase in pressure
D decrease in surface area
Higher pressure forces more gas molecules onto surface.
Physical adsorption is favored at
A high temperature, low pressure
B low temperature, high pressure
C high temperature, high pressure
D low temperature, low pressure
Weak forces are stabilized at low temperature.
Chemisorption involves
A weak van der Waals forces
B chemical bond formation
C multilayer formation
D low heat of adsorption
Chemisorption is specific and strong.
Freundlich adsorption isotherm fails at
A low pressure
B moderate pressure
C very high pressure
D room temperature
It does not predict saturation of surface.
Which adsorption is reversible
A chemisorption
B physical adsorption
C ionic adsorption
D selective adsorption
Weak forces allow reversibility.
Catalytic activity depends on
A mass of catalyst only
B surface area of catalyst
C color of catalyst
D density of catalyst
More surface area → more active sites.
Finely divided catalysts are more effective because
A they dissolve faster
B they have greater surface area
C they increase equilibrium constant
D they absorb heat
More adsorption sites available.
Promoters
A reduce activity of catalyst
B poison catalyst
C enhance activity of catalyst
D change reaction equilibrium
Promoters increase catalytic efficiency.
A catalyst poison works by
A increasing temperature
B blocking active sites
C lowering pressure
D increasing adsorption
Poison occupies surface sites permanently or strongly.
Enzymes are sensitive to
A pressure
B pH and temperature
C volume
D surface tension
Enzymes denature outside optimum conditions.
Colloidal particles do not settle due to
A gravity
B Brownian motion
C high density
D large size
Random motion counters gravitational settling.
Which method separates colloids from suspension
A dialysis
B filtration
C centrifugation
D evaporation
High-speed spinning separates larger particles.
Electrophoresis proves that colloidal particles
A are neutral
B are charged
C are very heavy
D are insoluble
Movement in electric field indicates charge.
A negatively charged sol is stabilized by
A Na⁺ ions
B Al³⁺ ions
C Cl⁻ ions
D SO₄²⁻ ions
Like-charged ions enhance stability.
Gold sol is prepared by
A dialysis
B dispersion method
C condensation method
D coagulation
Gold sol is prepared by chemical reduction.
Which colloid is lyophilic
A gold sol
B arsenic sulfide sol
C gelatin sol
D ferric hydroxide sol
Lyophilic sols have strong affinity for medium.
Which colloid is easily coagulated
A lyophilic sol
B hydrophilic sol
C lyophobic sol
D gelatin sol
Lyophobic sols are unstable.
Hardy–Schulze rule states that coagulating power depends on
A size of ion
B mass of ion
C charge of ion
D hydration energy
Higher valency ions have greater coagulating power.
A colloid which protects another colloid from coagulation is
A lyophobic colloid
B protective colloid
C emulsion
D aerosol
Forms a protective layer around particles.
The phenomenon of scattering of light by colloids is
A Brownian motion
B Tyndall effect
C electrophoresis
D dialysis
Visible light path is due to scattering.
Fog is an example of
A solid in gas
B liquid in gas
C gas in liquid
D solid in liquid
Water droplets dispersed in air.
Smoke is an example of
A liquid in gas
B gas in liquid
C solid in gas
D solid in liquid
Solid particles dispersed in air.
Foam is a colloid of
A gas in solid
B gas in liquid
C liquid in gas
D solid in liquid
Gas bubbles dispersed in liquid.
Jelly is an example of
A sol
B gel
C emulsion
D aerosol
Liquid dispersed in solid matrix.
Zeta potential indicates
A viscosity
B surface tension
C stability of colloid
D particle size
Higher zeta potential → greater stability.
Which process removes electrolytes from colloid
A centrifugation
B dialysis
C coagulation
D filtration
Semipermeable membrane removes ions.
Soap cleans dirt by
A adsorption
B coagulation
C emulsification
D precipitation
Soap emulsifies grease into water-soluble micelles.
Micelles are formed above
A boiling point
B freezing point
C critical micelle concentration
D osmotic pressure
Micelles form only above CMC.
Which is NOT a property of colloids
A Brownian motion
B Tyndall effect
C sedimentation
D adsorption
Colloids do not settle under gravity.
Colloids are intermediate between
A solids and liquids
B true solutions and suspensions
C gases and liquids
D mixtures and compounds
Particle size lies between the two.