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.
One mole of an ideal gas at 300 K occupies 24.6 L. The pressure of the gas is
A 1 atm
B 0.5 atm
C 2 atm
D 0.082 atm
At 300 K, molar volume ≈ 24.6 L at 1 atm for an ideal gas.
If pressure of a gas is reduced to one-fourth at constant temperature, its volume becomes
A one-fourth
B half
C four times
D unchanged
Boyle’s law: P ∝ 1/V. Reducing pressure to 1/4 increases volume 4 times.
A gas occupies 10 L at 27°C. Its volume at 127°C (pressure constant) is
A 12.5 L
B 13.3 L
C 15 L
D 20 L
T₁ = 300 K, T₂ = 400 K
V₂ = (10 × 400)/300 = 13.3 L
Which condition is essential for Boyle’s law to be applicable
A constant pressure
B constant volume
C constant temperature
D constant density
Boyle’s law relates pressure and volume at constant temperature.
The pressure exerted by gas molecules increases because
A volume increases
B molecular collisions increase
C molecular mass increases
D intermolecular attraction increases
Pressure is due to frequent collisions of gas molecules with container walls.
Which gas shows minimum deviation from ideal behavior
A NH₃
B CO₂
C H₂
D SO₂
H₂ has very weak intermolecular forces and small size → nearly ideal.
At very high temperature, real gases behave ideally because
A molecular size increases
B intermolecular attraction becomes negligible
C pressure becomes zero
D volume becomes infinite
High temperature increases kinetic energy, overcoming attractions.
Which term of van der Waals equation becomes negligible at low pressure
A a/V²
B b
C both a and b
D neither a nor b
At low pressure (large V), attraction term a/V² becomes very small.
The critical temperature of a gas depends on
A volume only
B pressure only
C intermolecular attraction
D density only
Stronger attraction → higher critical temperature.
Above critical temperature, a gas
A liquefies easily
B behaves as liquid
C cannot be liquefied by pressure
D solidifies directly
Above Tc, gas cannot be converted into liquid irrespective of pressure.
Average kinetic energy of gas molecules is proportional to
A pressure
B volume
C absolute temperature
D molar mass
KE ∝ T (Kelvin scale).
At same temperature, which gas has lowest rms speed
A H₂
B N₂
C O₂
D CO₂
Heavier gas has lower rms speed at same temperature.
If temperature is increased four times, rms speed becomes
A double
B four times
C half
D unchanged
u_rms ∝ √T → √4 = 2.
Which statement is true for ideal gases
A molecules attract strongly
B molecules have large volume
C collisions are elastic
D energy is lost in collisions
Ideal gas collisions are perfectly elastic.
Diffusion of gases occurs due to
A gravity
B pressure difference only
C random molecular motion
D surface tension
Random motion causes mixing of gases.
Surface tension is defined as force per unit
A mass
B volume
C area
D length
Surface tension = force acting per unit length along surface.
Which factor increases surface tension of a liquid
A increase in temperature
B addition of detergent
C decrease in temperature
D increase in impurities
Lower temperature strengthens cohesive forces → higher surface tension.
The reason insects can walk on water is
A density difference
B viscosity
C surface tension
D capillary rise
High surface tension of water supports insect weight.
Viscosity of liquids decreases with rise in temperature because
A density increases
B cohesive forces weaken
C pressure increases
D gravity decreases
Heating reduces intermolecular attractions.
SI unit of surface tension is
A dyne/cm
B poise
C N/m
D Pa•s
Newton per meter is the SI unit.
Which liquid shows highest surface tension
A water
B benzene
C mercury
D alcohol
Mercury has very strong cohesive forces.
Capillary rise is inversely proportional to
A surface tension
B density
C radius of capillary
D contact angle
Smaller radius → higher capillary rise.
When contact angle is 90°, capillary rise will be
A maximum
B minimum
C zero
D infinite
cos 90° = 0 → no rise or depression.
Which liquid does not wet glass
A water
B alcohol
C mercury
D glycerol
Cohesive force > adhesive force in mercury.
Viscosity of gases compared to liquids is
A much higher
B same
C much lower
D infinite
Gases have very weak intermolecular forces.
The number of nearest neighbors in FCC lattice is
A 6
B 8
C 10
D 12
FCC structure has coordination number 12.
Which lattice has highest packing efficiency
A simple cubic
B body-centered cubic
C face-centered cubic
D primitive cubic
FCC has ~74% packing efficiency.
A Frenkel defect is most common in crystals with
A large cation and anion
B small cation and large anion
C large cation only
D neutral atoms
Small cations easily move into interstitial sites.
Which defect decreases density of crystal
A Frenkel defect
B Schottky defect
C interstitial defect
D electronic defect
Missing ions reduce mass without changing volume.
Electrical conductivity in ionic solids increases due to
A Frenkel defect only
B Schottky defect only
C metal excess defect
D lattice vibrations only
Free electrons from F-centers enhance conductivity.
Which solid is anisotropic
A glass
B rubber
C quartz crystal
D plastic
Crystalline solids show direction-dependent properties.
Which solid has definite melting point
A rubber
B glass
C plastic
D NaCl
Crystalline solids melt sharply.
Which is an example of molecular solid
A NaCl
B diamond
C ice
D copper
Ice consists of discrete molecules held by hydrogen bonds.
Which solid conducts electricity in solid state
A NaCl
B diamond
C graphite
D ice
Graphite has delocalized electrons.
Coordination number of Na⁺ in NaCl is
A 4
B 6
C 8
D 12
NaCl has octahedral coordination.
Which defect causes crystal to become colored
A Frenkel defect
B Schottky defect
C F-center
D metal deficiency defect
Trapped electrons absorb visible light → color.
Which solid shows metallic bonding
A NaCl
B diamond
C copper
D ice
Metals have positive ions in a sea of electrons.
In BCC structure, coordination number is
A 6
B 8
C 10
D 12
BCC lattice has 8 nearest neighbors.
Which solid is non-stoichiometric
A NaCl
B KBr
C FeO
D CsCl
Transition metal oxides show metal deficiency.
Which crystal defect does not affect density significantly
A Schottky defect
B Frenkel defect
C metal excess defect
D interstitial defect
Ions remain within crystal → mass unchanged.
Which solid has covalent bonding throughout lattice
A NaCl
B copper
C diamond
D ice
Diamond has a 3-D covalent network.
Packing efficiency of simple cubic lattice is about
A 52%
B 68%
C 74%
D 90%
Simple cubic is least efficient.
The number of atoms per unit cell in FCC lattice is
A 2
B 3
C 4
D 6
8 corners (1) + 6 faces (3) = 4 atoms.
Which defect preserves electrical neutrality
A Frenkel defect
B Schottky defect
C both Frenkel and Schottky
D metal excess defect
Equal number of positive and negative ions involved.
Which solid is isotropic
A quartz
B diamond
C glass
D NaCl crystal
Amorphous solids have uniform properties in all directions.
Which property is shown by crystalline solids
A isotropy
B long-range order
C random arrangement
D indefinite melting point
Regular repeating arrangement is characteristic of crystals.
Which factor does not affect surface tension
A temperature
B nature of liquid
C impurities
D color of liquid
Color has no influence on intermolecular forces.
Which statement is true
A gases have highest viscosity
B liquids have highest viscosity
C solids have highest viscosity
D gases have lowest viscosity
Gases have weakest intermolecular forces.
Crystal lattice points represent
A atoms only
B ions only
C molecules only
D atoms, ions, or molecules
Lattice points can represent any constituent particle.
Amorphous solids are sometimes called
A true solids
B crystalline solids
C supercooled liquids
D ionic solids
Due to lack of long-range order and gradual softening.