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Solved: Energy is required to remove two electrons from Ca
Chapter , Problem 8.27(choose chapter or problem)
Energy is required to remove two electrons from Ca to form \(\mathrm{Ca}^{2+}\), and energy is required to add two electrons to \(\mathrm{O}\) to form \(\mathrm{O}^{2-}\). Yet \(\mathrm{CaO}\) is stable relative to the free elements. Which statement is the best explanation?
(a) The lattice energy of \(\mathrm{CaO}\) is large enough to overcome these processes.
(b) \(\mathrm{CaO}\) is a covalent compound, and these processes are irrelevant.
(c) \(\mathrm{CaO}\) has a higher molar mass than either \(\mathrm{Ca}\) or \(\mathrm{O}\).
(d) The enthalpy of formation of \(\mathrm{CaO}\) is small.
(e) \(\mathrm{CaO}\) is stable to atmospheric conditions.
Questions & Answers
QUESTION:
Energy is required to remove two electrons from Ca to form \(\mathrm{Ca}^{2+}\), and energy is required to add two electrons to \(\mathrm{O}\) to form \(\mathrm{O}^{2-}\). Yet \(\mathrm{CaO}\) is stable relative to the free elements. Which statement is the best explanation?
(a) The lattice energy of \(\mathrm{CaO}\) is large enough to overcome these processes.
(b) \(\mathrm{CaO}\) is a covalent compound, and these processes are irrelevant.
(c) \(\mathrm{CaO}\) has a higher molar mass than either \(\mathrm{Ca}\) or \(\mathrm{O}\).
(d) The enthalpy of formation of \(\mathrm{CaO}\) is small.
(e) \(\mathrm{CaO}\) is stable to atmospheric conditions.
ANSWER:
Step 1 of 2
To remove two electrons from calcium and add electrons to the oxygen to form respective ions, energy must be supplied.
However, The given ionic compound is more stable than the parent elements, Calcium and Oxygen.
This is because the calcium oxide ionic compound has very strong lattice strength \((3540 \mathrm{~kJ} /\) \(\mathrm{mol}\) ).
The process is exothermic, so ions are strongly attracted to each other because of its high positive value.