Q82 E - Chemistry (OpenStax)

Question

Which of the following compounds requires the most energy to convert one mole of the solid into separate ions? 

(a) \({\rm{MgO}}\) 

(b) \({\rm{SrO}}\) 

(c) \({\rm{KF}}\) 

(d) \({\rm{CsF}}\) 

(e) \({\rm{Mg}}{{\rm{F}}_{\rm{2}}}\)

Step-by-Step Solution

Answer

1. For \(MgO\) the amount energy required to convert one mole of the solid into separate ions will be greatest as compared to others.
2. For \(SrO\) the amount energy required to convert one mole of the solid into separate ions is lower as compared as to \(MgO\).
3. For \(KF\) the amount energy required to convert one mole of the solid into separate ions is lower as compared as to \(MgO\) and \(SrO\).
4. For \(CsF\) the amount energy required to convert one mole of the solid into separate ions is lower as compared as to \(MgO\) and \(SrO\).
5. For \({\rm{Mg}}{{\rm{F}}_{\rm{2}}}\) the amount energy required to convert one mole of the solid into separate ions is lower as compared as to \(MgO\) and \(SrO\).

Step 1: Concept Introduction

The lattice energy is the change of energy happening when 1 mole of a solid ionic compound forms in its gaseous state.

Step 2: Lattice Energy of Magnesium Oxide

Lattice energy is defined as energy that is required to convert the solid into separate ions and this can be explained on the basis of inter-ionic distance as well as by magnitude of charge present on ions.

\(MgO\) has smaller charge and \(Mg\) is smaller in size than \(Sr\). So, inter-sonic distance will be lower in \(MgO\). 

 

Therefore, the lattice energy of \(MgO\) is greater than \(SrO\).

Step 3: Lattice Energy of Strontium Oxide

Lattice energy is defined as energy that is required to convert the solid into separate ions and this can be explained on the basis of inter-ionic distance as well as by magnitude of charge present on ions. \(SrO\) has larger charge but \(Sr\) is greater in size than \(Mg\). So, inter-sonic distance will be higher in \(SrO\). 

 

Therefore, the lattice energy of \(SrO\) is less than \(MgO\).

Step 4: Lattice Energy of Potassium Fluoride

Lattice energy is defined as energy that is required to convert the solid into separate ions and this can be explained on the basis of inter-ionic distance as well as by magnitude of charge present on ions.

Since \(KF\) has lower charge than \(MgO\) and \(SrO\) therefore it will not have largest lattice energy.

 

Therefore, the lattice energy of \(KF\) is low.

Step 5: Lattice Energy of Caesium Fluoride

Lattice energy is defined as energy that is required to convert the solid into separate ions and this can be explained on the basis of inter-ionic distance as well as by magnitude of charge present on ions.

Since \(CsF\) has lower charge than \(MgO\) and \(SrO\) therefore it will not have largest lattice energy.

 

Therefore, the lattice energy of \(CsF\) is low.

Step 6: Lattice Energy of Magnesium Fluoride

Lattice energy is defined as energy that is required to convert the solid into separate ions and this can be explained on the basis of inter-ionic distance as well as by magnitude of charge present on ions.

Since \({\rm{Mg}}{{\rm{F}}_{\rm{2}}}\) has lower charge than \(MgO\) and \(SrO\) therefore it will not have largest lattice energy.

 

Therefore, the lattice energy of \({\rm{Mg}}{{\rm{F}}_{\rm{2}}}\) is low.