Born-Haber Cycle for LiF Formation
The Born-Haber cycle relates the standard enthalpy of formation ($\Delta H_f^\circ$) of an ionic compound to various thermodynamic quantities, including lattice enthalpy ($\Delta H_{\text{lattice}}^\circ$). The cycle allows us to calculate the lattice enthalpy using the following relationship:
$ \Delta H_f^\circ(\text{LiF}) = \Delta H_{\text{sub}}^\circ(\text{Li}) + \Delta H_{IE}^\circ(\text{Li}) + \frac{1}{2} \Delta H_{\text{diss}}^\circ(\text{F}_2) + \Delta H_{\text{EGE}}^\circ(\text{F}) + \Delta H_{\text{lattice}}^\circ(\text{LiF}) $
Calculating Lattice Enthalpy
We need to find the lattice enthalpy ($\Delta H_{\text{lattice}}^\circ(\text{LiF})$). Rearranging the Born-Haber equation:
$ \Delta H_{\text{lattice}}^\circ(\text{LiF}) = \Delta H_f^\circ(\text{LiF}) - \Delta H_{\text{sub}}^\circ(\text{Li}) - \Delta H_{IE}^\circ(\text{Li}) - \frac{1}{2} \Delta H_{\text{diss}}^\circ(\text{F}_2) - \Delta H_{\text{EGE}}^\circ(\text{F}) $
Substituting Given Values
Substitute the provided enthalpy values into the rearranged equation:
- Standard enthalpy of formation of LiF ($\Delta H_f^\circ(\text{LiF})$) = $-594 \text{ kJ mol}^{-1}$
- Enthalpy of sublimation of Li ($\Delta H_{\text{sub}}^\circ(\text{Li})$) = $155 \text{ kJ mol}^{-1}$
- Ionization enthalpy of Li ($\Delta H_{IE}^\circ(\text{Li})$) = $520 \text{ kJ mol}^{-1}$
- Enthalpy of dissociation of F₂ ($\Delta H_{\text{diss}}^\circ(\text{F}_2)$) = $150 \text{ kJ mol}^{-1}$, so $\frac{1}{2} \Delta H_{\text{diss}}^\circ(\text{F}_2) = 75 \text{ kJ mol}^{-1}$
- Electron gain enthalpy of F ($\Delta H_{\text{EGE}}^\circ(\text{F})$) = $-313 \text{ kJ mol}^{-1}$
Calculation:
$ \Delta H_{\text{lattice}}^\circ(\text{LiF}) = (-594) - (155) - (520) - (75) - (-313) $
$ \Delta H_{\text{lattice}}^\circ(\text{LiF}) = -594 - 155 - 520 - 75 + 313 $
$ \Delta H_{\text{lattice}}^\circ(\text{LiF}) = -1344 + 313 $
$ \Delta H_{\text{lattice}}^\circ(\text{LiF}) = -1031 \text{ kJ mol}^{-1} $
Magnitude of Lattice Enthalpy
The question asks for the magnitude of the lattice enthalpy.
Magnitude = $ |-1031 \text{ kJ mol}^{-1}| = 1031 \text{ kJ mol}^{-1} $
The magnitude of the lattice enthalpy of LiF is 1031 kJ mol⁻¹.
Similar Questions
- A 'p'-block element (E) and hydrogen form a binary cation $(\text{EH}_x)^+$, while $\text{EH}_3$ on treatment with $\text{K}_2\text{HgI}_4$ in alkaline medium gives a precipitate of basic mercury(II)amido-iodine. Given below are first ionisation enthalpy values ($\text{kJ mol}^{-1}$) for first element each from group 13, 14, 15 and 16. Identify the correct first ionisation enthalpy value for element E.
- $[\text{Ni}(\text{PPh}_3)_2\text{Cl}_2]$ is a paramagnetic complex. Identify the INCORRECT statements about this complex.
A. The complex exhibits geometrical isomerism.
B. The complex is white in colour.
C. The calculated spin-only magnetic moment of the complex is 2.84 BM.
D. The calculated CFSE (Crystal Field Stabilization Energy) of Ni in this complex is $-0.8 \, \Delta_0$.
E. The geometrical arrangement of ligands in this complex is similar to that in $\text{Ni(CO)}_4$.
Choose the correct answer from the options given below : - Given below are two statements :
Statement I : The first ionization enthalpy of Cr is lower than that of Mn.
Statement II : The second and third ionization enthalpies of Cr are higher than those of Mn.
In the light of the above statements, choose the correct answer from the options given below : - Among $\text{H}_2\text{S, H}_2\text{O, NF}_3, \text{NH}_3 \text{ and CHCl}_3$, identify the molecule (X) with lowest dipole moment value. The number of lone pairs of electrons present on the central atom of the molecule (X) is :
- Given below are two statements :
Statement I : Elements 'X' and 'Y' are the most and least electronegative elements, respectively among N, As, Sb and P. The nature of the oxides $\text{X}_2\text{O}_3$ and $\text{Y}_2\text{O}_3$ is acidic and amphoteric, respectively.
Statement II : $\text{BCl}_3$ is covalent in nature and gets hydrolysed in water. It produces $[\text{B(OH)}_4]^-$ and $[\text{B(H}_2\text{O)}_6]^{3+}$ in aqueous medium.
In the light of the above statements, choose the correct answer from the options given below : Given below are two statements :
Statement I : $\text{C} < \text{O} < \text{N} < \text{F}$ is the correct order in terms of first ionization enthalpy values.
Statement II : $\text{S} > \text{Se} > \text{Te} > \text{Po} > \text{O}$ is the correct order in terms of the magnitude of electron gain enthalpy values.
In the light of the above statements, choose the correct answer from the options given below :- Among the following oxides of 3d elements, the number of mixed oxides are _________.
$\text{Ti}_2\text{O}_3, \text{V}_2\text{O}_4, \text{Cr}_2\text{O}_3, \text{Mn}_3\text{O}_4, \text{Fe}_3\text{O}_4, \text{Fe}_2\text{O}_3, \text{Co}_3\text{O}_4$ - Consider three metal chlorides x, y and z, where x is water soluble at room temperature, y is sparingly soluble in water at room temperature and z is soluble in hot water. x, y and z are respectively
- In the Group analysis of cations, $\text{Ba}^{2+}$ & $\text{Ca}^{2+}$ are precipitated respectively as
- "X" is an oxoanion of the lightest element of group 7 (in the periodic table). The metal is in +6 oxidation state in "X". The color of the potassium salt of X is
Important Questions from Inorganic Chemistry
- A 'p'-block element (E) and hydrogen form a binary cation $(\text{EH}_x)^+$, while $\text{EH}_3$ on treatment with $\text{K}_2\text{HgI}_4$ in alkaline medium gives a precipitate of basic mercury(II)amido-iodine. Given below are first ionisation enthalpy values ($\text{kJ mol}^{-1}$) for first element each from group 13, 14, 15 and 16. Identify the correct first ionisation enthalpy value for element E.
- $[\text{Ni}(\text{PPh}_3)_2\text{Cl}_2]$ is a paramagnetic complex. Identify the INCORRECT statements about this complex.
A. The complex exhibits geometrical isomerism.
B. The complex is white in colour.
C. The calculated spin-only magnetic moment of the complex is 2.84 BM.
D. The calculated CFSE (Crystal Field Stabilization Energy) of Ni in this complex is $-0.8 \, \Delta_0$.
E. The geometrical arrangement of ligands in this complex is similar to that in $\text{Ni(CO)}_4$.
Choose the correct answer from the options given below : - Given below are two statements :
Statement I : The first ionization enthalpy of Cr is lower than that of Mn.
Statement II : The second and third ionization enthalpies of Cr are higher than those of Mn.
In the light of the above statements, choose the correct answer from the options given below : - Among $\text{H}_2\text{S, H}_2\text{O, NF}_3, \text{NH}_3 \text{ and CHCl}_3$, identify the molecule (X) with lowest dipole moment value. The number of lone pairs of electrons present on the central atom of the molecule (X) is :
- Given below are two statements :
Statement I : Elements 'X' and 'Y' are the most and least electronegative elements, respectively among N, As, Sb and P. The nature of the oxides $\text{X}_2\text{O}_3$ and $\text{Y}_2\text{O}_3$ is acidic and amphoteric, respectively.
Statement II : $\text{BCl}_3$ is covalent in nature and gets hydrolysed in water. It produces $[\text{B(OH)}_4]^-$ and $[\text{B(H}_2\text{O)}_6]^{3+}$ in aqueous medium.
In the light of the above statements, choose the correct answer from the options given below :
