Energy is required to remove two electrons from Ca to form Ca2+, and energy is required to add two electrons to O to form O2 - . Yet CaO is stable relative to the free elements. Which statement is the best explanation? (a) The lattice energy of CaO is large enough to overcome these processes. (b) CaO is a covalent compound, and these processes are irrelevant. (c) CaO has a higher molar mass than either Ca or O. (d) The enthalpy of formation of CaO is small. (e) CaO is stable to atmospheric conditions.

Video transcript

Hi everyone for this problem, we're told removing two electrons from magnesium to form a magnesium cat ion and adding two electrons to sulfur to form a sulfur and ion requires energy. However, magnesium sulfide is still relatively stable compared to free elements. Identify the statement that best explains this phenomenon. Okay, so magnesium sulfide is a ionic crystal because we have a cat ion and an an ion. So for this problem, we need to consider lattice energy and what lattice energy is is it's the energy released when two gaseous ions form one mole of an ionic crystal. And so as these opposite lee charged ions approach each other. The energy of interaction will be large and negative and this compensates for the ionization of the elements. And so in terms of all of the answer choices provided the last one, the lattice energy of magnesium sulfide is large enough to overcome the energy needed for the ionization of the elements is going to be the correct answer here. Okay, because we are considering lattice energy. That is the answer to this problem. And that's the end of this problem. I hope this was helpful