5.2 Energy Flashcards
Lattice enthalpies give an indication of the strength of ionic bonding
How would the lattice enthalpies of magnesium chloride and calcium chloride differ?
Explain your answer
(3 marks)
-lattice enthalpy of MgCl2 is more exothermic than CaCl2
-because magnesium ion (Mg2+ ) is smaller than calcium ions (Ca2+) or Mg2+ has a greater charge density
-therefore the attraction between Mg2+ and Cl- is greater (than between Ca2+ and Cl- )
Define the term lattice enthalpy
(2 marks)
-the enthalpy change that accompanies the FORMATION of ONE MOLE of an ionic compound from its GASEOUS IONS under standard conditions
The first ionisation energy of sodium is more endothermic than that of potassium
Explain why
(2 marks)
-sodium has a smaller atomic radius OR it has fewer shells
-therefore nuclear attraction increases
The lattice enthalpy of sodium oxide is more endothermic than that of potassium oxide
Explain why
(2 marks)
-Na+ ions are smaller
-Na+ has stronger attraction to O2-