Ionic Bonding & Lattice Energy
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All Questions for: Ionic Bonding & Lattice Energy
Question 1: An ionic bond is formed by:
- A Electrostatic attraction between oppositely charged ions
- B Sharing of electron pairs between atoms
- C Overlap of atomic orbitals
- D Delocalization of electrons in a metal lattice
Explanation: Ionic bonds result from the electrostatic attraction between oppositely charged ions formed when one atom transfers electrons to another.
Question 2: Which of the following pairs is most likely to form an ionic compound?
- A Potassium and chlorine
- B Carbon and oxygen
- C Nitrogen and nitrogen
- D Hydrogen and chlorine
Explanation: Ionic bonds form between metals with low ionization energy and nonmetals with high electron affinity. K (alkali metal) and Cl (halogen) form KCl, a classic ionic compound.
Question 3: Lattice energy is defined as:
- A The energy released when gaseous ions form one mole of an ionic solid
- B The energy required to melt an ionic solid
- C The energy required to remove an electron from an atom
- D The energy released when an electron is added to an atom
Explanation: Lattice energy is the energy released when one mole of an ionic solid forms from its gaseous ions, or equivalently the energy needed to separate one mole of the solid into gaseous ions.
Question 4: Lattice energy increases with:
- A Higher ionic charges and smaller ionic radii
- B Lower ionic charges and larger ionic radii
- C Larger ionic radii only
- D Lower ionic charges only
Explanation: According to Coulomb's law, lattice energy is proportional to the product of the ionic charges (q1·q2) divided by the interionic distance (r). Higher charges and smaller radii both increase lattice energy.
Question 5: Which compound has the highest lattice energy?
- A MgO
- B NaCl
- C KCl
- D NaF
Explanation: MgO has Mg²⁺ and O²⁻ ions with high charges and small radii, giving it a much larger lattice energy than compounds with +1/−1 charges such as NaCl, KCl, or NaF.
Question 6: Which of the following ionic compounds would be expected to have the highest melting point?
- A MgO
- B NaCl
- C KBr
- D NaI
Explanation: Higher lattice energy correlates with higher melting points. MgO (2+/2− charges, small radii) has the highest lattice energy among the given options, so it melts at the highest temperature.
Question 7: The Born-Haber cycle is used to determine:
- A The lattice energy of an ionic compound
- B The rate of an ionic reaction
- C The pH of a solution
- D The activation energy of a reaction
Explanation: The Born-Haber cycle applies Hess's law to calculate the lattice energy of an ionic compound from measurable quantities: sublimation, ionization, dissociation, electron affinity, and formation enthalpy.
Question 8: Which of the following is a property characteristic of ionic compounds?
- A They conduct electricity in the molten or aqueous state
- B They conduct electricity in the solid state
- C They have low melting points
- D They are typically gases at room temperature
Explanation: Ionic compounds conduct electricity when molten or dissolved (because ions are free to move), but not in the solid state (where ions are locked in the lattice).
Question 9: Ionic compounds typically dissolve in water because:
- A Water's high polarity stabilizes the ions, overcoming lattice energy
- B Water is non-polar
- C Water is a strong acid
- D Water reacts chemically with the ions
Explanation: Water is a polar solvent with a high dielectric constant. Its partial charges stabilize both cations (via oxygen lone pairs) and anions (via hydrogen atoms), and the ion-dipole interactions overcome lattice energy.
Question 10: The energy required to remove an electron from a gaseous atom is called:
- A Ionization energy
- B Electron affinity
- C Lattice energy
- D Bond dissociation energy
Explanation: Ionization energy is the minimum energy required to remove the most loosely bound electron from an isolated gaseous atom.
Question 11: The energy released when an electron is added to a gaseous atom is called:
- A Electron affinity
- B Ionization energy
- C Lattice energy
- D Electronegativity
Explanation: Electron affinity is the energy change (usually negative/released) when an electron is added to a neutral gaseous atom.
Question 12: The Born equation predicts that hydration enthalpy is proportional to:
- A z²/r (charge squared divided by radius)
- B z/r² (charge divided by radius squared)
- C z·r (charge times radius)
- D r/z (radius divided by charge)
Explanation: The Born equation gives ΔG_hydration ∝ -z²/r, where z is the ion charge and r its radius. Smaller, highly charged ions are more strongly hydrated.
Question 13: Which of the following ions has the smallest ionic radius?
- A Al³⁺
- B Na⁺
- C F⁻
- D O²⁻
Explanation: Isoelectronic ions: N³⁻, O²⁻, F⁻, Na⁺, Mg²⁺, Al³⁺ all have 10 electrons. Higher positive charge pulls the electron cloud closer, so Al³⁺ has the smallest ionic radius.
Question 14: Which is the correct formula for the ionic compound formed from calcium and nitride ions?
- A Ca₃N₂
- B CaN
- C Ca₂N₃
- D Ca₃N
Explanation: Ca forms Ca²⁺ and nitride is N³⁻. Charge balance requires 3 Ca²⁺ and 2 N³⁻ to give neutrality: Ca₃N₂.
Question 15: Which of the following statements about ionic solids is FALSE?
- A They deform easily under mechanical stress
- B They are hard and brittle
- C They have high melting points
- D They are poor electrical conductors in the solid state
Explanation: Ionic solids are typically hard and brittle, but they shatter (not deform) under stress because the ions are rigidly ordered. The claim that they deform easily is false.
Question 16: Which factor most strongly affects the solubility of an ionic compound in water?
- A Balance between lattice energy and hydration energy
- B Molecular mass only
- C Crystal color
- D Nature of the cation only
Explanation: Solubility depends on the balance between the lattice energy (favoring the solid) and the hydration energies of the ions (favoring dissolution). When hydration dominates, the salt dissolves.
Question 17: Which of the following compounds is LEAST likely to exist as an ionic solid?
- A CCl₄
- B NaCl
- C KBr
- D MgO
Explanation: Ionic character depends on electronegativity difference. CCl₄ is covalent (small ΔEN, nonpolar solvent-like properties). The others are predominantly ionic (metal + nonmetal).
Question 18: The strength of an ionic bond is inversely related to:
- A The distance between the ions
- B The charges on the ions
- C The dielectric constant of the medium
- D The atomic masses of the ions
Explanation: According to Coulomb's law (F ∝ q₁·q₂/r²), force is inversely related to the square of the distance between ions. Larger ions produce weaker ionic bonds.
Question 19: An ionic bond is most likely formed between elements with:
- A A large electronegativity difference
- B Similar electronegativities
- C Identical electronegativities
- D The same ionization energies
Explanation: Large electronegativity differences (typically >1.7) favor electron transfer from a metal (low electronegativity) to a nonmetal (high electronegativity), producing ions.
Question 20: Which ionic compound is expected to be the most soluble in water?
- A MgSO₄
- B BaSO₄
- C CaSO₄
- D SrSO₄
Explanation: Solubility of alkaline earth sulfates decreases down the group (BeSO₄ > MgSO₄ > CaSO₄ > BaSO₄) because lattice energy decreases more slowly than hydration energy. MgSO₄ is much more soluble than BaSO₄.
Question 21: The lattice enthalpy of an ionic solid can be estimated using:
- A The Kapustinskii or Born-Landé equation
- B The Nernst equation
- C The Henderson-Hasselbalch equation
- D The van der Waals equation
Explanation: The Kapustinskii equation (like the Born-Landé equation) estimates lattice enthalpy from charges and ionic radii. The Born-Landé and Kapustinskii equations are standard textbook methods.
Question 22: In the Born-Haber cycle for NaCl, which step requires energy input?
- A Ionization of Na and dissociation of Cl₂
- B Formation of NaCl lattice
- C Electron affinity of Cl
- D Sublimation of Na only
Explanation: Removing an electron from Na (ionization energy) and dissociating Cl₂ require energy. Sublimation of Na and ionization of Na are endothermic; Cl₂ bond breaking is endothermic; Cl electron affinity and lattice formation are exothermic.
Question 23: Which of the following has the greatest ionic character?
- A KF
- B HCl
- C HBr
- D HI
Explanation: Ionic character correlates with electronegativity difference. Among these, KF has the largest ΔEN (K 0.82, F 3.98 → ΔEN ≈ 3.16), making it the most ionic.
Question 24: Fajans' rules predict that a covalent bond is more likely when:
- A The cation is small and highly charged and the anion is large and polarizable
- B Both ions are large and singly charged
- C The cation is large and the anion is small
- D Both ions have the same electronegativity
Explanation: Fajans' rules: high cation charge, small cation size, and large anion size all favor polarization of the anion by the cation, giving more covalent character. LiI satisfies all three.
Question 25: Which of the following pairs of ions would form the strongest ionic bond?
- A Al³⁺ and O²⁻
- B Na⁺ and Cl⁻
- C K⁺ and Br⁻
- D Cs⁺ and I⁻
Explanation: Lattice energy ∝ (q₁q₂)/r. Al³⁺ and O²⁻ have the highest charges (3+/2−) and relatively small radii, so Al₂O₃ has exceptionally strong ionic bonding.