Question

79. The lattice energy of LiF is 1023 kJ/mol, and the Li-F distance is 201 pm. MgO crystallizes in the same structure as LiF but with a Mg-O distance of 205 pm. Which of the following values most closely approximates the lattice energy of MgO: 256 kJ/mol, 512 kJ/mol, 1023 kJ/mol, 2046 kJ/mol, or 4008 kJ/mol? Explain your choice.​

Answer 1

The lattice energy of LiF is 1023 kJ/mol, and the Li-F distance is 201 pm. MgO crystallizes in the same structure as LiF but with a Mg-O distance of 205 pm. Most closely approximates the lattice energy of MgO is 4008 kJ/mol.

The lattice energy which is represented as the delta(H) lattice of an ionic compound is defined as the energy associated with the separation of one mole of the solid into its constituent gaseous ions.

The lattice energy of the ionic compound is given as

ΔH=C×Z+(Z-)/R

Where,

C is constant for the crystal structure.

Z+ Z-are charges on cation and anion ..

R is the interionic distance.

For LiF,

LiF dissociated as,

LiF→Li+ +F-

Here Z+ Z-are 1 .

R=201 pm

ΔH=1023 kJ/mol

C=1023×201/1

As MgO hasn't the same crystal structure as LiF, z the value of C will be the same for MgO as like in LiF.

Magnesium oxide is dissociated as

MgO- Mg^2+ +O^2-

ΔH=1023×201×2×2/205 pm

ΔH=4008 kJ/mol

The lattice energy of MgO is 4008 kJ/mol

Learn more about lattice energy at:

brainly.com/question/18222315

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