Concept explainers
Calculate the lattice energy of
Interpretation:
The lattice energy of
Concept introduction:
Lattice energy is defined as the amount of energy needed to convert a mole of a solid ionic compound to its respective gaseous ions.
The lattice energy of
Here,
Answer to Problem 20QP
Solution:
Explanation of Solution
Given information: The value of
The value of
The value of
The value of
The value of
The value of
The lattice energy of
Substitute the value
The lattice energy of themolecule
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Chapter 8 Solutions
Chemistry
- Define the term lattice energy. Why, energetically, do ionic compounds form? Fig. 3-8 illustrates the energy changes involved in the formation of MgO(s) and NaF(s). Why is the lattice energy of MgO(s) so different from that of NaF(s)? The magnesium oxide is composed of Mg2+ and O2 ions. Energetically, why does Mg2+O2 form and not Mg+O? Why doesnt Mg3+O3 form?arrow_forwardUsing the standard enthalpy of formation data in Appendix G, calculate the bond energy of the carbon-sulfur double bond in CS2.arrow_forwardArrange the following series of compounds in order of increasing lattice energies. (a) NaBr, NaCl, KBr (b) MgO, CaO, CaCl2 (c) LiF, BeF2, BeOarrow_forward
- Bond Enthalpy When atoms of the hypothetical element X are placed together, they rapidly undergo reaction to form the X2 molecule: X(g)+X(g)X2(g) a Would you predict that this reaction is exothermic or endothermic? Explain. b Is the bond enthalpy of X2 a positive or a negative quantity? Why? c Suppose H for the reaction is 500 kJ/mol. Estimate the bond enthalpy of the X2 molecule. d Another hypothetical molecular compound, Y2(g), has a bond enthalpy of 750 kJ/mol, and the molecular compound XY(g) has a bond enthalpy of 1500 kJ/mol. Using bond enthalpy information, calculate H for the following reaction. X2(g)+Y2(g)2XY(g) e Given the following information, as well as the information previously presented, predict whether or not the hypothetical ionic compound AX is likely to form. In this compound, A forms the A+ cation, and X forms the X anion. Be sure to justify your answer. Reaction: A(g)+12X2(g)AX(s)The first ionization energy of A(g) is 400 kJ/mol. The electron affinity of X(g) is 525 kJ/mol. The lattice energy of AX(s) is 100 kJ/mol. f If you predicted that no ionic compound would form from the reaction in Part e, what minimum amount of AX(s) lattice energy might lead to compound formation?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_forwardThe 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_forward
- The equation for the combustion of gaseous methanol is 2 CH3OH(g) + 3 O2(g) 2 CO2(g) + 4 H2O(g) (a) Using the bond dissociation enthalpies in Table 8.8, estimate the enthalpy change for this reaction. What is the enthalpy of combustion of one mole of gaseous methanol? (b) Compare your answer in part (a) with the value of tHcalculated using enthalpies of formation data.arrow_forwardFor each of the following, write an equation that corresponds to the energy given. a. lattice energy of NaCl b. lattice energy of NH4Br c. lattice energy of MgS d. O9O double bond energy beginning with O2(g) as a reactantarrow_forwardCompare your answers from parts a and b of Exercise 69 of Chapter 3 with H values calculated for each reaction using standard enthalpies of formation in Appendix 4. Do enthalpy changes calculated from bond energies give a reasonable estimate of the actual values?arrow_forward
- Explain the decomposition of nitroglycerin in terms of relative bond enthalpies.arrow_forwardhat is the enthalpy change for a process? Is enthalpy a state function? In what experimental apparatus are enthalpy changes measured?arrow_forwardThink of forming an ionic compound as three steps (this is a simplification, as with all models): (I) removing an electron from the metal; (2) adding an electron to the nonmetal; and (3) allowing the metal cation and nonmetal anion to come together. a. What is the sign of the energy change for each of these three processes? b. In general, what is the sign of the sum of the first two processes? Use examples to support your answer. c. What must be the sign of the sum of the three process d. Given your answer to part c, why do ionic bonds occur? e. Given your above explanations, why is NaCl stable but not Na2Cl? NaCl2? What about MgO compared to MgO2? Mg2O?arrow_forward
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