A real gas shows ideal behavior most closely at
A high pressure and low temperature
B low pressure and high temperature
C high pressure and high temperature
D low pressure and low temperature
At low pressure and high temperature, molecules are far apart and attractions become negligible → ideal behavior.
In van der Waals equation, the correction term for pressure is
A P + a/V²
B P − a/V²
C P + b
D P − b
Attractive forces reduce observed pressure, so corrected pressure is increased by adding a/V².
In van der Waals equation, volume correction is written as
A V + b
B V − b
C V + a
D V − a
Real gas molecules occupy volume, so free volume is less; corrected volume is (V − b).
Which quantity increases when temperature increases (for fixed gas)
A average kinetic energy
B intermolecular attraction
C van der Waals constant b
D critical temperature
Average kinetic energy of gas molecules is directly proportional to absolute temperature.
For a fixed mass of gas, if pressure and temperature are both doubled, volume becomes
A double
B unchanged
C half
D four times
From PV/T = constant → V ∝ T/P. Doubling both T and P keeps V same.
At constant volume, if temperature is doubled, pressure becomes
A half
B double
C four times
D unchanged
Gay-Lussac’s law: P ∝ T at constant volume.
The gas law relating pressure and temperature at constant volume is
A Boyle’s law
B Charles’ law
C Gay-Lussac’s law
D Avogadro’s law
It states P/T = constant when volume and moles are constant.
Which of the following has highest critical temperature
A H₂
B He
C CO₂
D Ne
Stronger intermolecular attractions raise critical temperature; CO₂ has much higher Tc than light noble gases/H₂.
Gas deviates most from ideality near
A critical temperature
B very high temperature only
C very low pressure only
D zero volume only
Near Tc, attractions and compressibility effects become significant causing high deviation.
If Z = PV/nRT is less than 1, it indicates dominance of
A repulsive forces
B attractive forces
C no forces at all
D only gravitational forces
Attractions reduce pressure and hence PV becomes smaller → Z < 1.
For the same gas, u₍rms₎ at 400 K compared to 100 K is
A 1/2
B 2
C 4
D 1/4
u_rms ∝ √T. √(400/100)=√4=2.
Rate of diffusion is maximum for gas having
A highest molar mass
B lowest molar mass
C highest density always
D highest boiling point always
Graham’s law: rate ∝ 1/√M → lighter gases diffuse faster.
If a gas diffuses 4 times faster than another, its molar mass is
A 16 times more
B 4 times more
C 16 times less
D 4 times less
r₁/r₂ = √(M₂/M₁). If r₁=4r₂ → 16 = M₂/M₁ → M₁ = M₂/16.
The correct relation between average speed and rms speed is
A u_avg > u_rms
B u_rms > u_avg
C u_avg = u_rms always
D u_rms = 0
u_rms is always slightly greater than u_avg for Maxwell distribution.
The kinetic theory assumption about gas molecules is
A they attract strongly at all times
B they have negligible volume compared to container
C they are stationary
D they occupy fixed positions
Ideal gas assumes molecular volume negligible relative to container.
Surface tension of a liquid is due to
A gravitational force only
B unbalanced cohesive forces
C ionic bonding only
D presence of solute only
Surface molecules experience inward cohesive forces resulting in surface tension.
Which will decrease surface tension of water
A adding detergent
B cooling water
C increasing pressure
D adding pure mercury
Detergent reduces surface tension, improving wetting.
Which statement about viscosity of liquids is correct
A it increases with temperature
B it decreases with temperature
C it becomes infinite at high temperature
D it is independent of temperature
Higher temperature reduces intermolecular attractions and lowers viscosity.
Which has maximum viscosity among these
A water
B ethanol
C glycerol
D acetone
Strong hydrogen bonding makes glycerol very viscous.
Capillary rise is proportional to
A radius of capillary
B surface tension / radius
C density / radius
D radius / surface tension
h=2γcosθρgrh = \frac{2\gamma \cos\theta}{\rho g r}h=ρgr2γcosθ → h ∝ γ/r.
Capillary rise will be maximum when contact angle θ is
A 0°
B 90°
C 180°
D 120°
cosθ is maximum at θ=0°, making capillary rise maximum.
A liquid will not wet a solid surface if
A adhesion > cohesion
B cohesion > adhesion
C surface tension = 0
D temperature = 0
If cohesive forces dominate, liquid forms droplets and does not spread (e.g., mercury on glass).
The meniscus of water in glass capillary is
A convex
B concave
C flat
D irregular
Water wets glass (adhesion > cohesion), producing concave meniscus.
The meniscus of mercury in glass capillary is
A concave
B convex
C flat
D no meniscus
Mercury does not wet glass (cohesion > adhesion), giving convex meniscus.
Which is correct about viscosity of gases
A decreases with temperature
B increases with temperature
C independent of temperature
D becomes zero at high temperature
In gases, higher temperature increases molecular speed and momentum transfer → higher viscosity.
Coordination number in simple cubic lattice is
A 4
B 6
C 8
D 12
Each atom touches 6 nearest neighbors in SC structure.
In FCC lattice, the number of atoms per unit cell is
A 2
B 3
C 4
D 6
FCC: corners contribute 1 + faces contribute 3 → total 4 atoms per unit cell.
In BCC lattice, number of atoms per unit cell is
A 1
B 2
C 4
D 6
BCC has 1 atom from corners + 1 body-centered atom = 2.
Packing efficiency order is
A FCC > BCC > SC
B SC > BCC > FCC
C BCC > FCC > SC
D FCC > SC > BCC
FCC (74%) > BCC (68%) > SC (52%).
A defect where cations are missing and anions are also missing in equal number is
A Frenkel defect
B Schottky defect
C interstitial defect
D metal excess defect
Schottky defect involves equal vacancies of cations and anions.
A defect involving vacancy and interstitial simultaneously is
A Schottky defect
B Frenkel defect
C line defect
D surface defect
In Frenkel defect, an ion leaves its lattice site and occupies interstitial site.
Which defect is common in AgCl
A Schottky defect
B Frenkel defect
C metal deficiency defect
D vacancy defect only
Ag⁺ is small and can move into interstitial position, causing Frenkel defect.
Schottky defect is common in
A NaCl
B ZnS
C AgBr
D CuI
Schottky defect occurs in ionic crystals with similar sized ions like NaCl, KCl, CsCl.
Which defect causes a crystal to become colored due to trapped electrons
A Frenkel defect
B Schottky defect
C F-center defect
D interstitial defect
Electrons trapped in anion vacancies (F-centers) absorb visible light → color.
A metal excess defect due to anion vacancy is shown by
A NaCl
B KCl
C NaBr
D NaCl heated in Na vapor
Na atoms donate electrons; anion vacancies trap electrons → F-centers.
A crystal showing metal deficiency defect is usually
A NaCl
B FeO
C KBr
D CsCl
Transition metal oxides like FeO show metal deficiency (non-stoichiometric).
Which statement is correct about amorphous solids
A show long-range order
B show sharp melting point
C are isotropic
D always conduct electricity
Amorphous solids have random arrangement, so properties are same in all directions.
A crystalline solid is anisotropic because
A it has irregular surface
B it has long-range periodic arrangement
C it is always soft
D it absorbs water
Different directions in lattice have different arrangement → anisotropy.
In NaCl crystal, coordination number of Na⁺ is
A 4
B 6
C 8
D 12
NaCl has octahedral holes; each Na⁺ is surrounded by 6 Cl⁻.
In CsCl structure, coordination number of Cs⁺ is
A 4
B 6
C 8
D 12
CsCl has cubic coordination; each Cs⁺ is surrounded by 8 Cl⁻.
Which type of solid has highest melting point generally
A molecular solid
B ionic solid
C covalent network solid
D metallic solid
Covalent network solids (diamond, SiC) have strong covalent bonds throughout lattice → very high melting point.
Which is an example of covalent network solid
A I₂
B Ice
C Diamond
D CO₂ (dry ice)
Diamond has 3D covalent network.
Which solid is held by van der Waals forces mainly
A NaCl
B Diamond
C Dry ice
D Copper
CO₂ molecules in dry ice are held by weak dispersion forces.
Which statement is correct about ionic solids
A conduct electricity in solid state
B conduct electricity in molten state
C are soft and volatile
D are always colored
In molten state, ions are free to move, enabling conduction.
Which defect does not affect density significantly
A Schottky defect
B Frenkel defect
C metal deficiency defect
D metal excess defect
Ions remain within crystal, only displaced → total mass nearly unchanged → density unaffected.
Which structure has maximum coordination number
A SC
B BCC
C FCC
D Diamond cubic
FCC has coordination number 12 (maximum among given).
Which packing gives closest packing
A simple cubic
B body-centered cubic
C face-centered cubic
D primitive tetragonal
FCC and HCP are closest-packed structures (74% packing).
Number of atoms in a simple cubic unit cell is
A 1
B 2
C 3
D 4
8 corners × 1/8 = 1 atom per unit cell.
Density of ionic crystal decreases due to
A Frenkel defect
B Schottky defect
C interstitial defect
D electronic defect only
Vacancies reduce number of ions → mass decreases while volume same → density decreases.
Crystal lattice is
A random arrangement of particles
B periodic 3D arrangement of particles
C arrangement only on surface
D arrangement only in 2D
Lattice is an ordered three-dimensional repeating pattern of points/particles.