At constant temperature, pressure of a gas is doubled. Its volume becomes
A four times
B half
C double
D unchanged
Boyle’s law states P ∝ 1/V at constant temperature. If pressure doubles, volume becomes half.
If volume of a gas is 2 L at 300 K, its volume at 600 K (pressure constant) is
A 1 L
B 2 L
C 3 L
D 4 L
By Charles’ law, V₁/T₁ = V₂/T₂ → V₂ = (2 × 600)/300 = 4 L.
One mole of an ideal gas occupies 22.4 L at
A 273 K and 1 atm
B 300 K and 1 atm
C 273 K and 2 atm
D 0 K and 1 atm
Standard Temperature and Pressure (STP) = 273 K, 1 atm.
The number of moles of gas present in 11.2 L at STP is
A 0.25
B 0.5
C 1.0
D 2.0
22.4 L = 1 mol → 11.2 L = 0.5 mol.
The pressure exerted by a gas is due to
A attraction between molecules
B repulsion between molecules
C collision of molecules with container walls
D gravitational force
According to kinetic theory, pressure arises from molecular collisions with walls.
Which quantity remains constant in Boyle’s law
A Volume
B Pressure
C Temperature
D Density
Boyle’s law applies at constant temperature for fixed mass of gas.
Which law explains behavior of gas mixture
A Boyle’s law
B Dalton’s law
C Graham’s law
D Henry’s law
Dalton’s law deals with partial pressures of gases in a mixture.
Partial pressure of a gas depends on
A total pressure only
B mole fraction and total pressure
C temperature only
D volume only
Partial pressure = mole fraction × total pressure.
The SI unit of gas constant R is
A L•atm•mol⁻¹•K⁻¹
B J•mol⁻¹•K⁻¹
C cal•mol⁻¹•K⁻¹
D Pa•L•K⁻¹
SI unit of R = 8.314 J•mol⁻¹•K⁻¹.
Ideal gas equation fails at
A low pressure and high temperature
B high pressure and low temperature
C low pressure only
D high temperature only
At high P and low T, intermolecular forces and volume become significant.
The average kinetic energy of gas molecules is independent of
A temperature
B pressure
C volume
D nature of gas
KE depends only on temperature, not on nature of gas.
Which gas has the same average kinetic energy at the same temperature
A Only H₂
B Only CO₂
C All gases
D Only O₂
At a given temperature, all gases have the same average kinetic energy.
The most probable speed of gas molecules depends on
A temperature only
B molar mass only
C temperature and molar mass
D pressure only
vmp∝T/Mv_{mp} \propto \sqrt{T/M}vmp∝T/M.
The order of speeds is
A rms > average > most probable
B most probable > rms > average
C average > rms > most probable
D rms > most probable > average
For any gas: u_rms > u_avg > u_mp.
Which gas deviates most from ideal behavior
A He
B H₂
C NH₃
D Ne
NH₃ shows hydrogen bonding and strong intermolecular attraction.
Compressibility factor Z is less than 1 when
A repulsive forces dominate
B attractive forces dominate
C gas behaves ideally
D temperature is very high
Attractions reduce pressure → Z < 1.
The value of Z is greater than 1 when
A attractive forces dominate
B repulsive forces dominate
C pressure is very low
D temperature is very high
Repulsions increase pressure → Z > 1.
Critical pressure is the pressure required to liquefy a gas at
A 0 K
B STP
C critical temperature
D boiling point
Critical pressure corresponds to liquefaction at Tc.
At critical point, distinction between liquid and gas
A increases
B disappears
C becomes maximum
D remains constant
At critical point, liquid and gas phases become indistinguishable.
Liquefaction of gases is favored by
A low pressure and high temperature
B high pressure and low temperature
C low pressure and low temperature
D high temperature only
Cooling and compression bring molecules closer to liquefy.
Viscosity of a liquid is mainly due to
A repulsive forces
B gravitational force
C intermolecular attraction
D ionic bonding
Stronger attractions cause higher resistance to flow.
Which liquid has highest viscosity at room temperature
A Water
B Ethanol
C Glycerol
D Acetone
Glycerol has strong hydrogen bonding → high viscosity.
Viscosity of gases increases with temperature because
A intermolecular attraction increases
B molecular speed increases
C density increases
D surface tension increases
Faster molecules transfer momentum more effectively → higher viscosity.
Surface tension is measured in SI units of
A N/m
B Pa•s
C J/mol
D atm
SI unit of surface tension is Newton per meter.
The liquid with strongest surface tension is
A Benzene
B Water
C Mercury
D Alcohol
Strong cohesive forces between mercury atoms give very high surface tension.
Which phenomenon explains spherical shape of small liquid drops
A Viscosity
B Surface tension
C Capillary action
D Density
Surface tension minimizes surface area, forming spheres.
Capillary depression is observed in
A water in glass tube
B mercury in glass tube
C oil in cotton
D ink in paper
Mercury does not wet glass → cohesive force dominates → depression.
Which factor does not affect capillary rise
A radius of capillary
B surface tension
C density of liquid
D color of liquid
Color has no effect on capillary action.
The temperature at which surface tension becomes zero is called
A boiling point
B melting point
C critical temperature
D freezing point
At Tc, liquid and gas become identical → no surface tension.
Detergents help in cleaning because they
A increase surface tension
B decrease surface tension
C increase viscosity
D increase density
Lower surface tension improves wetting of surfaces.
Which solid has sharp melting point
A Glass
B Rubber
C Plastic
D NaCl
Crystalline solids melt at a fixed temperature.
Which solid is isotropic
A Diamond
B Quartz
C NaCl crystal
D Glass
Amorphous solids show same properties in all directions.
Which unit cell has highest packing efficiency
A Simple cubic
B Body-centered cubic
C Face-centered cubic
D Primitive cell
FCC (and HCP) have packing efficiency ≈ 74%.
Coordination number of simple cubic lattice is
A 4
B 6
C 8
D 12
Each atom in SC touches 6 neighbors.
The packing efficiency of simple cubic structure is approximately
A 52%
B 68%
C 74%
D 90%
Simple cubic has lowest packing efficiency.
Which defect leads to electrical conductivity in solids
A Frenkel defect
B Schottky defect
C Metal excess defect
D Vacancy defect
Extra electrons released in metal excess defect enhance conductivity.
Which defect occurs when anion vacancies are occupied by electrons
A Frenkel defect
B Schottky defect
C Metal excess defect due to anion vacancy
D Metal deficiency defect
Electrons trapped in anion vacancies act as F-centers.
Which solid shows Frenkel defect
A NaCl
B KCl
C AgBr
D CsCl
Small cation Ag⁺ easily occupies interstitial positions.
Schottky defect is shown by
A ZnS
B AgCl
C NaCl
D CdS
Schottky defect common in ionic solids with similar-sized ions.
Which defect maintains electrical neutrality
A Frenkel defect
B Schottky defect
C Both Frenkel and Schottky
D Metal excess defect
Equal number of cations and anions involved → neutrality preserved.
Non-stoichiometric solids are those which
A follow exact formula
B have fixed composition
C show variable composition
D are amorphous
Non-stoichiometric solids deviate from ideal chemical formula.
Which solid is a p-type semiconductor
A Ge doped with As
B Si doped with P
C Si doped with B
D Ge doped with Sb
Trivalent dopant creates holes → p-type semiconductor.
n-type semiconductor contains excess of
A electrons
B holes
C neutrons
D protons
Pentavalent doping provides free electrons.
Which solid is covalent network solid
A NaCl
B I₂
C Diamond
D Ice
Diamond has 3D network of covalent bonds.
Which solid is molecular solid
A NaCl
B Diamond
C Ice
D Copper
Ice consists of discrete H₂O molecules held by hydrogen bonding.
Metallic solids conduct electricity due to
A holes only
B ions only
C free electrons
D covalent bonds
Delocalized electrons allow electrical conduction.
Which crystal defect lowers density
A Frenkel defect
B Schottky defect
C Metal excess defect
D Interstitial defect
Missing ions reduce mass without changing volume → density decreases.
Which crystal shows anisotropy
A Glass
B Plastic
C Rubber
D Quartz
Crystalline solids show direction-dependent properties.
Which property is common to all crystalline solids
A Isotropy
B Long-range order
C Irregular shape
D Variable melting point
Regular repeating arrangement defines crystalline solids.
Which solid softens over a range of temperature
A NaCl
B Diamond
C Quartz
D Glass
Amorphous solids do not have sharp melting point.