8.83 Construct a Born-Haber cycle for the formation of the hy- pothetical compound NaCl2, where the sodium ion has a 2+ charge (the second ionization energy for sodium is given in Table 7.2). (a) How large would the lattice energy need to be for the formation of NaCl2 to be exothermic? (b) If we were to estimate the lattice energy of NaCl2 to be roughly equal to that of MgCl2 (2326 kJ/mol from Table 8.1), what value would you obtain for the standard enthalpy of formation, AH, of NaCl2? ing together of Na (g) and Cl (AH=-788 kJ/mol). Notice Table 8.1 lists the lattice energies for a number of ionic compounds. The large itive values indicate that the ions are strongly attracted to one another in ionic solid Pos TABLE 8.1 Lattice Energies for Some Ionic Compounds Lattice Energy (kJ/mol) Lattice Energy (kJ/mo Compound 2526 Compound MgCl2 1030 2127 LiF SrCl2 834 LiCl 730 Lil 3795 MgO 910 NaF 3414 CaO 788 NaCl 3217 SrO 732 NaBr 682 Nal ScN 7547 KF 808 КС. 701 KBr 671 CsCl 657 CsI 600

8.83 Construct a Born-Haber cycle for the formation of the hy- pothetical compound NaCl2, where the sodium ion has a 2+ charge (the second ionization energy for sodium is given in Table 7.2). (a) How large would the lattice energy need to be for the formation of NaCl2 to be exothermic? (b) If we were to estimate the lattice energy of NaCl2 to be roughly equal to that of MgCl2 (2326 kJ/mol from Table 8.1), what value would you obtain for the standard enthalpy of formation, AH, of NaCl2? ing together of Na (g) and Cl (AH=-788 kJ/mol). Notice Table 8.1 lists the lattice energies for a number of ionic compounds. The large itive values indicate that the ions are strongly attracted to one another in ionic solid Pos TABLE 8.1 Lattice Energies for Some Ionic Compounds Lattice Energy (kJ/mol) Lattice Energy (kJ/mo Compound 2526 Compound MgCl2 1030 2127 LiF SrCl2 834 LiCl 730 Lil 3795 MgO 910 NaF 3414 CaO 788 NaCl 3217 SrO 732 NaBr 682 Nal ScN 7547 KF 808 КС. 701 KBr 671 CsCl 657 CsI 600

Chemistry for Engineering Students

4th Edition

ISBN:9781337398909

Author:Lawrence S. Brown, Tom Holme

Publisher:Lawrence S. Brown, Tom Holme

Chapter7: Chemical Bonding And Molecular Structure

Section: Chapter Questions

Problem 7.74PAE: 7.74 In a lattice, a positive ion is often surrounded by eight negative ions. We might reason,...

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Construct a Born–Haber cycle for the formation of the hypotheticalcompound NaCl2, where the sodium ion has a 2+charge (the second ionization energy for sodium is given inTable 7.2). (a) How large would the lattice energy need to befor the formation of NaCl2 to be exothermic? (b) If we wereto estimate the lattice energy of NaCl2 to be roughly equalto that of MgCl2 (2326 kJ/mol from Table 8.1), what valuewould you obtain for the standard enthalpy of formation,ΔHf°, of NaCl2?
Aluminum oxide (Al₂ O₃) is a widely used industrial abrasive(emery, corundum), for which the specific application depends onthe hardness of the crystal. What does this hardness imply about the magnitude of the lattice energy? Would you have predictedfrom the chemical formula that Al₂ O₃ is hard? Explain.
(a) Based on the lattice energies of MgCl2 and SrCl2 given inTable 8.1, what is the range of values that you would expectfor the lattice energy of CaCl2? (b) Using data from AppendixC, Figure 7.11, Figure 7.13, and the value of the secondionization energy for Ca, 1145 kJ>mol, calculate the latticeenergy of CaCl2.
Which ionic compounds would have the greatestlattice energy: NaCl, KCl, or MgC l 2 ? Explain youranswer.
Which Compound has the largest lattice energy, KCl CaCl2 Na2O or MgO?
We can define average bond enthalpies and bond lengthsfor ionic bonds, just like we have for covalent bonds. Whichionic bond is predicted to have the smaller bond enthalpy,Li—F or Cs—F?
lattice energy of sodium fluroide NaF is -908 . Pairs Na+/Ca2+ and F-/O2- having roughlu same ionic radii. What is tge lattice energy of CaO?
(a) Does the lattice energy of an ionic solid increase or decrease (i) as the charges of the ions increase, (ii) as the sizes of the ions increase? (b) Arrange the following substances not listed in Table 8.2 according to their expected lattice energies, listing them from lowest lattice energy to the highest: MgS, KI, GaN, LiBr. Table 8.2
Arrange the following ionic compounds in order of decreasing lattice energy: RbI, NaCl, KBr, LiF, MgS, BeO, BN. Arrange the following anions in order of increasing ionic radii: F-, O2-, N3-, P3-, As3-, Ge4- Arrange the following cations in order of increasing ionic radii: Fr+, Cs+, Rb+, B3+, Al3+, Ga3+
The magnitude of the lattice energy (energy required to separate the ions) for the compounds K2O and CaO are shown below with respect to Coulombic attraction, which is the best explanation for the difference in lattice energy?
Place the following in order of decreasing magnitude of lattice energy. Explain your answer. K2O Rb2S Li2O
The electron affinity of oxygen is -141kj/mol, corresponding to the reaction O(g)+e-—>O-(g) The lattice energy of K2O(s) is 2238kj/mol.Use these data along with data in Appendix C and figure 7.10 to calculate the “second electron affinity” of oxygen, corresponding to the reaction O-(g)+e-—>O2-(g)