Enthalpy of solution and hydration Quiz
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5 questions, one answer each
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1. Which equation represents the enthalpy of hydration of the chloride ion?
- A. Cl⁻(g) + aq → Cl⁻(aq)
- B. Cl⁻(aq) → Cl⁻(g) + aq
- C. ½Cl₂(g) + e⁻ → Cl⁻(g)
- D. NaCl(s) + aq → Na⁺(aq) + Cl⁻(aq)
2. The enthalpy of lattice formation of KBr is −679 kJ mol⁻¹. The enthalpies of hydration of K⁺ and Br⁻ are −322 and −335 kJ mol⁻¹. What is the enthalpy of solution of KBr?
- A. −22 kJ mol⁻¹
- B. −1336 kJ mol⁻¹
- C. +1336 kJ mol⁻¹
- D. +22 kJ mol⁻¹
3. Why is the enthalpy of hydration of Mg²⁺ more exothermic than that of Ca²⁺?
- A. Mg²⁺ is smaller, so it has a higher charge density
- B. Mg²⁺ has a smaller charge
- C. Mg²⁺ has a larger ionic radius
- D. Mg²⁺ is hydrated by more covalent bonds
4. Why is the hydration of gaseous ions exothermic?
- A. Covalent bonds in water break
- B. The lattice breaks up
- C. Ion–dipole attractions form with water molecules
- D. The ions gain electrons
5. An ionic compound has ΔHsol = +12 kJ mol⁻¹ and lattice formation enthalpy −780 kJ mol⁻¹. The cation has ΔHhyd = −400 kJ mol⁻¹. What is ΔHhyd of the anion?
- A. +368 kJ mol⁻¹
- B. −368 kJ mol⁻¹
- C. −1168 kJ mol⁻¹
- D. −1192 kJ mol⁻¹