Concept explainers
Use the Born-Haber cycle outlined in Section 9.3 for LiF to calculate the lattice energy of NaCl. [The heat of sublimation of Na is 108 kJ/mol and ΔH°f(NaCl ) = −411 kJ/mol. Energy needed to dissociate
Interpretation:
Using the Born-Haber cycle for
Concept Introduction:
Born-Haber cycle is based on Hess’s law to calculate the lattice enthalpy of ionic compounds and deals with energy changes in formation of ionic compounds.
The energy released when gaseous state ions of unlike charges that are infinitely farther apart combine to form a stable ionic solid is called Lattice energy. Conversely, the energy required to break the electrostatic force of attraction between the ions of unlike charges in the ionic solid and revert them to gaseous state is also termed as Lattice energy of an ionic solid.
Hess’s law is applied to calculate the enthalpy changes in a reaction. According to Hess’s law – “The overall enthalpy change of a reaction is equal to the sum of the enthalpy changes involving in each and every individual steps in the reaction”. Thus if a reaction involves ‘n’ steps then enthalpy change
Answer to Problem 9.25QP
Lattice energy of
Explanation of Solution
Given data:
The first step of Born-Haber cycle involves sublimation of solid
The second step of Born-Haber cycle involves dissociation of gaseous
The third step of Born-Haber cycle is ionization of gaseous
The fourth step of Born-Haber cycle is ionization of gaseous
The fifth and final step of Born-Haber cycle is formation of solid
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Chapter 9 Solutions
Chemistry
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- The standard enthalpies of formation for S(g), F(g), SF4(g), and SF6(g) are + 278.8, + 79.0, 775, and 1209 kJ/mol, respectively. a. Use these data to estimate the energy of an SF bond. b. Compare your calculated value to the value given in Table 8.5. What conclusions can you draw? c. Why are the Ht0 values for S(g) and F(g) not equal to zero, since sulfur and fluorine are elements?arrow_forwardCalculate the lattice energy of potassium fluoride, KF, using the BornHaber cycle. Use thermodynamic data from Appendix C to obtain the enthalpy changes for each step. (Note: You will obtain a slightly different answer if you use values given in Chapter 8 for the ionization energy and electron affinity, which are energy values at 0 K rather than the enthalpy changes at 298 K.)arrow_forwardWhich of the following compounds requires the most energy to convert one mole of the solid into separate ions? (a) MgO (b) SrO (c) KF (d) CsF (e) MgF2arrow_forward
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