Tag: lattice energy

Questions Related to lattice energy

Which has larger lattice energy among $ZnO$ and $NaCl$?

chemistry lattice energy defining lattice energy ionic or electrovalent bond energy cycles

  1. $ZnO$ > $NaCl$

  2. $ZnO$ < $NaCl$

  3. $ZnO$ = $NaCl$

  4. None of these

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Correct Option: A
Explanation:

Lattice Energy is directly proportional to the charge on the ions and inversely proportional to the size of the ions. There are two factors at work here. The main factor is the charge on the ions. In $ZnO$, both positive and negative ions carry two charges. In $NaCl$, they only carry one. The lattice energy is much greater in $ZnO$ than in $NaCl$.

The addition of energy in the form of heat causes molecules or crystals of the substance to break up into ions.

chemistry lattice energy defining lattice energy ionic or electrovalent bond energy cycles

  1. True

  2. False

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Correct Option: A
Explanation:

The breaking up of a compound into simpler constituents that are usually capable of recombining under other conditions. In electrolytic, or ionic, dissociation, the addition of a solvent or of energy in the form of heat causes molecules or crystals of the substance to break up into ions (electrically charged particles).

Which shows the highest lattice energy?

chemistry lattice energy defining lattice energy ionic or electrovalent bond energy cycles

  1. $RbF$

  2. $CsF$

  3. $NaF$

  4. $KF$

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Correct Option: C
Explanation:

$NaF$  shows the highest lattice energy.Smaller the size of cation, more is attraction among ions. The bond between ions of opposite charge is strongest when the ions are small.The lattice energies for the alkali metal halides is therefore, largest.

Based on lattice energy and other considerations which one of the following alkali metal chloride has the highest melting point ?

chemistry lattice energy defining lattice energy ionic or electrovalent bond energy cycles

  1. $KCl$

  2. $RhCl$

  3. $LiCl$

  4. $NaCl$

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Correct Option: D
Explanation:

Comparison of melting points of ionic compounds is generally done by considering the following two factors:

  1. Charge of the cation/anion  : More the charge of cation or anion, stronger will be the forces of attraction between the ions and higher will be the melting point.
  2. Ionic radii: More the distance between ions, lesser will be the strength of the bond giving rise to lesser melting point.                                              
Going by the above rules, the order should have been:
LiCl > NaCl > KC l> RbCl  
(Since charges of the ions are same for each molecule and cationic radius increases down the group.)
But $LiCl$, due to excessive polarization, exhibits high covalent character and is placed last in the order. Hence, the new order would be:
NaCl > KCl > RbCl > LiCl
The other ions, being similar in size to chloride ions, do not undergo much polarization.

Which compound processes the greatest lattice energy?

chemistry lattice energy defining lattice energy ionic or electrovalent bond energy cycles

  1. $LiBr$

  2. $LiCl$

  3. $LiI$

  4. $LiF$

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Correct Option: D
Explanation:

Among the halides of lithium, $LiF$ has highest lattice energy due to similar sizes of cation and anion which results in efficient packing in the crystal structure.

Select the correct order of lattice energy.

chemistry lattice energy defining lattice energy ionic or electrovalent bond energy cycles

  1. $LiF\, <\, LiBr\, <\, LiI$

  2. $LiCl\, >\, LiBr\, >\, LiI$

  3. $LiCl\, >\, NaCl\, >\, KCl$

  4. $BeCO _3\, <\, MgCO _3\, <\, SrCO _3\, <\, BaCO _3$

Show answer
Correct Option: B,C
Explanation:

The lattice energy decreases in the order $LiCl\, >\, LiBr\, >\, LiI$. 

As the size of the anion increases from chloride to iodide, the lattice energy decreases.
The lattice energy decreases in the order $LiCl\, >\, NaCl\, >\, KCl$. 
As the size of the cation increases from lithium to potassium, the lattice energy decreases.

Lattice energy of ionic compounds depend upon:

chemistry lattice energy defining lattice energy ionic or electrovalent bond energy cycles

  1. packing of ions only

  2. charge and size of ions

  3. charge on ion only

  4. size of ions only

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Correct Option: B
Explanation:

Lattice energy is defined as the heat of formation for ions of opposite charge in the gas phase to combine into an ionic solid. It is directly proportional to the charge on the ions and inversely proportional to the size of the ions. 

Which of the following compounds will have the largest lattice energy?

chemistry lattice energy defining lattice energy ionic or electrovalent bond energy cycles

  1. $AlBr _3$

  2. $CaO$

  3. $LiBr$

  4. $MgBr _2$

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Correct Option: A
Explanation:

Among the cations, $Al^{3+},\ Ca^{2+},\ Li^{+}$ and $Mg^{2+}$, $Al^{3+}$ has the highest charge. Hence, $AlBr _3$ has the highest lattice energy. The lattice energy is directly proportional to the charge on the ion and inversely proportional to the size of the ion. 

The lattice energies of the oxidies of $Mg,Ca,Sr \;$ and $\;Ba$ follow the order:

chemistry lattice energy defining lattice energy ionic or electrovalent bond energy cycles

  1. $BaO\;>\;SrO\;>\;CaO\;>MgO$

  2. $CaO\;>\;BaO\;>\;SrO\;>\;MgO$

  3. $MgO\;>\;SrO\;>\;CaO\;>\;BaO$

  4. $MgO\;>\;CaO\;>\;SrO\;>\;BaO$
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Correct Option: D

The order of increasing lattice energy of the following compounds is :

chemistry lattice energy defining lattice energy ionic or electrovalent bond energy cycles

  1. $NaCl\;<\;CaO\;<\;NaBr\;<\;BaO$

  2. $NaBr\;<\;NaCl\;<\;BaO\;<\;CaO$

  3. $NaCl\;<\;NaBr\;<\;BaO\;<\;CaO$

  4. $NaBr\;<\;NaCl\;<\;CaO\;<\;BaO$

Show answer
Correct Option: B