The value of universal gas constant (R) in L•atm•mol⁻¹•K⁻¹ is
A 0.0821
B 8.314
C 1.987
D 22.4
R = 0.0821 L•atm•mol⁻¹•K⁻¹ (also equals 8.314 J•mol⁻¹•K⁻¹ in SI).
Boyle’s law is valid when temperature is
A constant
B increasing
C decreasing
D zero
Boyle’s law: at constant temperature, P ∝ 1/V for a fixed mass of gas.
Charles’ law relates volume with
A pressure
B temperature
C density
D viscosity
At constant pressure, volume is directly proportional to absolute temperature (V ∝ T).
Avogadro’s law states that equal volumes of gases at same T and P contain equal number of
A molecules
B atoms
C moles of solvent
D ions
Equal volumes of gases at same T and P have equal number of molecules (or moles).
The combined gas law is
A PV = constant
B V/T = constant
C P/T = constant
D PV/T = constant
For fixed moles of gas: PV/T remains constant when conditions change.
The equation PV = nRT is called
A Dalton’s law
B Ideal gas equation
C Graham’s law
D Henry’s law
It combines Boyle, Charles, and Avogadro laws into a single relation.
STP molar volume of an ideal gas is approximately
A 11.2 L
B 18.0 L
C 22.4 L
D 24.0 L
At STP (0°C, 1 atm), 1 mol ideal gas occupies ~22.4 L.
At constant pressure, if temperature is doubled (in Kelvin), volume becomes
A half
B double
C one-fourth
D unchanged
By Charles’ law, V ∝ T (in Kelvin).
Dalton’s law is related to
A partial pressures
B diffusion speed
C osmotic pressure
D surface tension
Total pressure of gas mixture equals sum of partial pressures of each gas.
The unit of pressure in SI is
A atmosphere
B bar
C pascal
D mmHg
SI unit: Pascal (Pa) = N/m².
Average kinetic energy of gas molecules is directly proportional to
A pressure only
B volume only
C absolute temperature
D molar mass
Average KE ∝ T (Kelvin) for an ideal gas.
Root mean square speed (u₍rms₎) is proportional to
A √T and inversely proportional to √M
B T and inversely proportional to M
C √M and inversely proportional to √T
D independent of temperature
urms=3RTMu_{rms} = \sqrt{\frac{3RT}{M}}urms=M3RT.
At the same temperature, which gas has highest rms speed
A H₂
B N₂
C O₂
D CO₂
Lighter gas has higher speed at same temperature.
Real gases deviate from ideal behavior mainly due to
A absence of mass
B molecular attractions and finite volume
C presence of light
D zero temperature
Ideal gas assumes no intermolecular forces and zero molecular volume, which is not true in real gases.
The compressibility factor Z for ideal gas is
A 0
B 1
C 2
D depends on temperature
Z = PV/(nRT). For ideal gas, Z = 1.
Van der Waals equation corrects ideal gas equation for
A viscosity only
B surface tension only
C intermolecular attraction and molecular volume
D diffusion only
It introduces constants ‘a’ (attraction) and ‘b’ (volume correction).
In van der Waals equation, constant ‘a’ accounts for
A molecular volume
B intermolecular attraction
C temperature correction
D pressure unit conversion
‘a’ corrects pressure due to attractions reducing effective pressure.
In van der Waals equation, constant ‘b’ represents
A attractive forces
B excluded volume (molecular size)
C kinetic energy
D diffusion rate
‘b’ accounts for finite volume occupied by gas molecules.
A gas behaves most ideally 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 P and high T, molecules are far apart and attractions are negligible.
The critical temperature of a gas is the temperature above which
A it freezes
B it can’t be liquefied by pressure alone
C its density becomes zero
D pressure becomes zero
Above Tc, no matter how high pressure is applied, gas won’t liquefy.
Graham’s law relates rate of diffusion to
A pressure
B molar mass
C volume
D viscosity
Rate ∝ 1/√M; lighter gases diffuse faster.
If M₁ = 4 and M₂ = 16, then r₁/r₂ is
A 1/2
B 2
C 4
D 1/4
r1/r2=M2/M1=16/4=2r_1/r_2=\sqrt{M_2/M_1}=\sqrt{16/4}=2r1/r2=M2/M1=16/4=2.
Effusion refers to
A liquid flowing in a tube
B gas passing through a tiny hole into vacuum
C solid melting
D gas dissolving in liquid
Effusion is escape of gas molecules through a pinhole.
At same T, which gas effuses faster
A NH₃
B HCl
C CO₂
D SO₂
Lowest molar mass (17) → highest effusion rate.
Surface tension arises due to
A repulsion among molecules only
B unbalanced cohesive forces at surface
C gravitational force only
D ionic bonding only
Surface molecules experience net inward cohesive force, creating surface tension.
Surface tension of a liquid generally
A increases with temperature
B decreases with temperature
C remains constant always
D becomes infinite at high temperature
Higher temperature weakens cohesive forces, lowering surface tension.
Viscosity is a measure of
A ability to flow easily
B resistance to flow
C surface area
D compressibility
Higher viscosity means greater internal friction against flow.
Viscosity of liquids generally
A increases with temperature
B decreases with temperature
C remains constant always
D becomes zero near room temperature
Heating reduces intermolecular attractions and lowers viscosity.
The SI unit of viscosity (dynamic viscosity) is
A poise
B pascal-second
C dyne/cm
D atm
SI unit: Pa•s (also written as N•s•m⁻²).
Capillary rise is maximum when
A surface tension is high and radius is small
B surface tension is low and radius is large
C density is high and radius is large
D gravity is zero only
Capillary rise h∝γrh \propto \frac{\gamma}{r}h∝rγ. Smaller r and higher γ increase rise.
Liquid rises in capillary tube when
A cohesive force > adhesive force
B adhesive force > cohesive force
C adhesive force = 0
D surface tension = 0
If adhesion to glass is stronger, liquid wets the surface and rises (like water).
Mercury shows convex meniscus because
A adhesive force > cohesive force
B cohesive force > adhesive force
C surface tension is zero
D density is low
Mercury does not wet glass; cohesion dominates → convex meniscus.
A crystalline solid has
A random arrangement of particles
B long-range order
C no melting point
D indefinite shape always
Crystals show regular repeating arrangement throughout the solid.
Amorphous solids are best described as
A true crystals
B supercooled liquids with short-range order
C having sharp melting point
D always ionic
Amorphous solids lack long-range order and soften over a range of temperature.
Which solid shows anisotropy
A Glass
B Rubber
C Crystalline quartz
D Plastic
Crystals show direction-dependent properties (anisotropy).
Which is an example of amorphous solid
A NaCl crystal
B Diamond
C Glass
D Quartz
Glass lacks long-range order → amorphous.
A unit cell is
A the whole crystal
B smallest repeating unit of crystal lattice
C a molecule of crystal
D defect in crystal
Repetition of unit cell in 3D builds the crystal lattice.
In a simple cubic unit cell, number of atoms per unit cell is
A 1
B 2
C 4
D 6
8 corner atoms × (1/8 contribution each) = 1 atom total.
In a body-centered cubic (BCC) unit cell, number of atoms per unit cell is
A 1
B 2
C 4
D 8
Corners contribute 1 atom + 1 atom at body center = 2.
In a face-centered cubic (FCC) unit cell, number of atoms per unit cell is
A 2
B 3
C 4
D 6
Corners = 1 atom, faces: 6×(1/2)=3 atoms → total 4.
Coordination number in BCC structure is
A 4
B 6
C 8
D 12
In BCC, each atom touches 8 nearest neighbors.
Coordination number in FCC structure is
A 4
B 6
C 8
D 12
In FCC (and HCP), coordination number is 12.
Packing efficiency in FCC is approximately
A 52%
B 68%
C 74%
D 100%
Close-packed structures (FCC/HCP) have packing efficiency ~74%.
Packing efficiency in BCC is approximately
A 52%
B 68%
C 74%
D 88%
BCC packing efficiency is about 68%.
A point defect where ions are missing from their normal sites is
A Frenkel defect
B Schottky defect
C Interstitial defect
D Line defect
Schottky defect: equal number of cations and anions missing → vacancies.
A defect where an ion leaves its site and occupies interstitial position is
A Schottky defect
B Frenkel defect
C Metal excess defect
D Non-stoichiometric defect
Frenkel defect involves displacement of ion to interstitial site (vacancy + interstitial).
Schottky defect decreases
A density of crystal
B melting point always increases
C mass always increases
D electrical conductivity always decreases
Vacancies reduce number of ions per unit volume, lowering density.
Frenkel defect generally does not change density because
A ions disappear completely
B ions move within the crystal
C new ions are added from outside
D unit cell expands infinitely
Ion shifts from lattice site to interstitial site; total ions remain same → density nearly unchanged.
An example of Frenkel defect is
A NaCl
B CsCl
C AgCl
D KBr
Frenkel defect common in crystals with small cation like Ag⁺ (AgCl, AgBr, ZnS).
The intermolecular forces mainly responsible for high boiling point of water are
A London forces only
B Dipole–dipole forces only
C Hydrogen bonding
D Ionic bonding
Strong H-bonding in water increases boiling point and many unusual properties.