Q.1
Correct Option: B) 40°C (MP), 214°C (BP)
Explanation: A solid at room temperature (~25°C) must have a melting point (MP) above 25°C. Option B (MP = 40°C) fits this criterion, while others are gases (A/C) or liquids (D) at room temperature.
Q.2
Correct Option: A) Ar < HCl < HI
Explanation: Boiling points increase with molecular weight and intermolecular forces: Ar (nonpolar, weakest London forces) < HCl (polar, dipole-dipole) < HI (largest molar mass, strongest London forces).
Q.3
Correct Option: C) Covalent bond
Explanation: Covalent bonds are intramolecular (within molecules), while the other options are intermolecular forces (London forces = A/B, dipole-dipole = D).
Q.4
Correct Option: C) Increase in volume
Explanation: At higher temperatures (T₂ > T₁), gas molecules move faster, occupying more space. This shifts the isotherm away from axes on a P-V diagram, indicating increased volume at constant pressure.
Q.5
Correct Option: D) Both ‘A’ and ‘B’
Explanation: Real gases deviate from ideality due to intermolecular attractions (A) and non-negligible molecular volume (B), especially at high pressures/low temperatures.
Q.6
Correct Option: D) Carbon tetrachloride (BP = 76.5°C)
Explanation: Higher boiling points correlate with lower vapor pressure. CCl₄ has the highest BP, indicating strongest intermolecular forces (London forces) and lowest vapor pressure at room temperature.
Q.7
Correct Option: C) Increase four times
Explanation: Using the combined gas law (P₁V₁/T₁ = P₂V₂/T₂), if T₂ = 2T₁ and P₂ = ½P₁, then V₂ = 4V₁.
Q.8
Correct Option: D) HF is stronger acid than HI
Explanation: HI is stronger than HF because I⁻ is more stable than F⁻ (larger size, weaker H-bonding). HF’s strength is limited by its high bond enthalpy.
Q.9
Correct Option: D) Amount of liquid
Explanation: Evaporation rate depends on surface area (A), temperature (B), and intermolecular forces (C), but not the total quantity of liquid (D).
Q.10
Correct Option: D) Like ions come in front of each other on applying external force
Explanation: Ionic crystals are brittle because mechanical force aligns like-charged ions, causing repulsion and fracture.
Q.11
Correct Option: B) Boron nitride
Explanation: Boron nitride forms layered covalent solids (similar to graphite), unlike diamond (3D network), AlN, or SiC (which are harder, non-layered covalent solids).
Q.12
Correct Option: C) Silicon carbide
Explanation: SiC is a covalent solid and insulator, while brass (A), graphite (B), and bronze (D) are metallic conductors.
Q.13
Correct Option: B) High polarizability
Explanation: Larger alkanes have more electrons, leading to stronger London dispersion forces (polarizability) and higher boiling points.
Q.14
Correct Option: C) The boiling point of water decreases at mountain
Explanation: Lower atmospheric pressure at high altitudes reduces water’s boiling point, slowing cooking.
Q.15
Correct Option: A) High vapour pressure at given temperature
Explanation: Liquids with high vapor pressure boil more easily (lower BP) because molecules escape the liquid phase more readily.
Q.16
Correct Option: C) Rate of collision is increased
Explanation: At higher temperatures, molecules collide more frequently and energetically with container walls, increasing pressure (Gay-Lussac’s law).
Q.17
Correct Option: A) Temperature and pressure
Explanation: For ideal gases, Vₘ = RT/P (molar volume depends only on T and P, not molecular properties).
Q.18
Correct Option: A) 5P₁
Explanation: Using P₁V₁/T₁ = P₂V₂/T₂: V₂ = 10V₁, T₂ = 2T₁ (Kelvin) → P₂ = P₁/5.
Q.19
Correct Option: A) 8
Explanation: In NaCl’s FCC unit cell, each Na⁺ is surrounded by 6 Cl⁻ and vice versa, but there are 8 equidistant oppositely charged ions in the 3D lattice.
Q.20
Correct Option: B) Molecular
Explanation: Molecular solids (e.g., ice, dry ice) have weak intermolecular forces, making them soft with low MPs, unlike ionic/covalent/metallic solids.
Q.21
Correct Option: D) Both “A” and “B”
Explanation: At high T, increased kinetic energy (A) overcomes intermolecular attractions (B), making gas behavior more ideal (PV/RT ≈ 1).
Q.22
Correct Option: D) H₂O
Explanation: Water has the highest BP due to extensive hydrogen bonding (stronger than HF’s or ethanol’s).
Q.23
Correct Option: C) London dispersion forces
Explanation: London forces exist in all atoms/molecules (due to temporary dipoles), while others require permanent dipoles (B/D) or H-bonding (A).
Q.24
Correct Option: A) Water
Explanation: Water’s strong H-bonding gives it the lowest vapor pressure (highest boiling point) among the options.
Q.25
Correct Option: B) Their conductivity increases with temperature
Explanation: Metallic conductivity decreases with temperature (due to lattice vibrations), unlike semiconductors.
Q.26
Correct Option: B) Molecular
Explanation: Lattices occupied by covalent molecules (e.g., I₂, CO₂) are molecular solids, held by weak van der Waals forces.
Q.27
Correct Option: C) 1%
Explanation: Dipole-dipole forces are ~1% as strong as covalent bonds (~1–10 kJ/mol vs. ~100–400 kJ/mol).
Q.28
Correct Option: D) All of the above
Explanation: Density (d) = PM/RT, so it depends on M (A), P (B), and V (C, since d ∝ 1/V).
Q.29
Correct Option: D) 6.022×10²²
Explanation: At STP, 1 mole (22.4 dm³) contains 6.022×10²³ molecules → 1 dm³ has 6.022×10²³/22.4 ≈ 2.688×10²² molecules.
Q.30
Correct Option: D) Pm = dR/T
Explanation: The correct forms are PV=nRT, P=(dRT)/M, or PV=mRT/M. Option D rearranges incorrectly.
Q.31
Correct Option: B) Density
Explanation: Under same T/P, gases have equal volumes (A), KE (C), and mean square velocity (D), but densities (B) vary with molar mass.
Q.32
Correct Option: D) High temperature, Low pressure
Explanation: High T and low P minimize intermolecular forces and molecular volume effects, making gases behave ideally.
Q.33
Correct Option: B) Doubled
Explanation: From PV = nRT, doubling n at constant V/T doubles P.
Q.34
Correct Option: B) 62400 dm³ K⁻¹ mol⁻¹
Explanation: R = 0.0821 atm·dm³·K⁻¹·mol⁻¹ (D) or 8.314 J·K⁻¹·mol⁻¹ (C). Option B’s value is incorrect.
Q.35
Correct Option: D) PV = nRT
Explanation: This is the ideal gas equation. Others are incorrect or rearranged improperly.
Q.36
Correct Option: B) PM/RT
Explanation: From PV = nRT and n = m/M, density (d = m/V) = PM/RT.
Q.37
Correct Option: D) Boyle’s, Charles’s, and Avogadro’s laws
Explanation: The ideal gas law combines these three: Boyle (P ∝ 1/V), Charles (V ∝ T), Avogadro (V ∝ n).
Q.38
Correct Option: C) He > H₂ > CO₂
Explanation: Smaller, nonpolar gases (He, H₂) behave more ideally than larger/polar ones (CO₂) due to weaker intermolecular forces.
Q.39
Correct Option: B) Significant increase in intermolecular attractive forces
Explanation: At low T, reduced kinetic energy allows attractive forces to dominate, causing deviation from ideality.
Q.40
Correct Option: B) London < Dipole-Dipole < Hydrogen bonding
Explanation: Interaction strength order: London (weakest) < dipole-dipole < H-bonding (strongest).
Q.41
Correct Option: A) Ions don’t have translatory motion
Explanation: In solid state, ions are fixed in the lattice. Conductivity occurs when ions move (e.g., in molten/aqueous states).
Q.42
Correct Option: D) Solubility in polar solvents
Explanation: Ionic solids dissolve in polar solvents (like water) due to ion-dipole interactions. They are insulators when solid (B) and have low vapor pressure (A/C).
Q.43
Correct Option: B) Rate of evaporation = rate of condensation
Explanation: Vapor pressure is measured at dynamic equilibrium, where evaporation and condensation rates balance.
Q.44
Correct Option: A) Water > Ethanol > Acetone
Explanation: Boiling points: Water (100°C, strong H-bonds) > Ethanol (78°C, weaker H-bonds) > Acetone (56°C, dipole-dipole only).
Q.45
Correct Option: C) Exothermic process
Explanation: Evaporation is endothermic (absorbs heat to overcome intermolecular forces), causing cooling (D). It occurs at the surface (A) and is continuous (B).
Q.46
Correct Option: A) Surface area
Explanation: Vapor pressure depends on temperature (C), intermolecular forces (B), and liquid nature (D), but not surface area (A).
Q.47
Correct Option: B) ½ times
Explanation: From Charles’s Law (V ∝ T at constant P), cooling from 273°C (546K) to 0°C (273K) halves the volume.
Q.48
Correct Option: A) Boiling point of H₂O rises
Explanation: A pressure cooker increases internal pressure, raising water’s boiling point and accelerating cooking.
Q.49
Correct Option: B) Less energy than steam
Explanation: Steam at 100°C has additional latent heat of vaporization, making its energy content higher than liquid water at the same temperature.
Q.50
Correct Option: B) CdI₂
Explanation: CdI₂ has significant covalent character (Fajans’ rule: large anion, polarizing cation), unlike purely ionic NaCl, AlF₃, or MgO.
