Concept explainers
Interpretation: The
Concept introduction: The change in energy of a reaction is defined as the sum of change in the internal energy of a system and the product of its absolute temperature and entropy.
Electron affinity is defined as the energy released from a neutral atom in gaseous phase when it gains an electron to form negatively charged ion.
Ionization energy is defined as the energy required to remove an electron from the neutral atom.
To determine: The analogy between the electron affinity of fluorine and ionization energy of sodium; if the
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Chemistry: An Atoms First Approach
- Bromine-containing species play a role in environmental chemistry. For example, they are evolved in volcanic eruptions. (a) The following molecules are important in bromine environmental chemistry: HBr, BrO, and HOBr. Which is an odd-electron molecule? (b) Use bond dissociation enthalpies to estimate rH for three reactions of bromine: Br2(g) 2 Br(g) 2 Br(g) + O2(g) 2 BrO(g) BrO(g) + H2O(g) HOBr(g) + OH(g) (c) Using bond dissociation enthalpies, estimate the standard enthalpy of formation of HOBr(g) from H2(g), O2(g), and Br2(g). (d) Are the reactions in parts (b) and (c) exothermic or endothermic?arrow_forwardThe 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_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
- Given the following data calculate H for the reaction On the basis of the enthalpy change, is this a useful reaction for the synthesis of ammonia?arrow_forwardEstimate H for the following reactions using bond energies given in Table 8.5. 3CH2=CH2(g) + 3H2(g) 3CH2CH3(g) The enthalpies of formation for C6H6(g) and C6H12 (g) are 82.9 and 90.3 kJ/mol. respectively. Calculate H for the two reactions using standard enthalpies of formation from Appendix 4. Account for any differences between the results obtained from the two methods.arrow_forwardDinitrogen monoxide, N2O, can decompose to nitrogen and oxygen gas: 2 N2O(g) 2 N2(g) + O2(g) Use bond dissociation enthalpies to estimate the enthalpy change for this reaction.arrow_forward
- Hydrogenation reactions, which involve the addition of H2 to a molecule, are widely used in industry to transform one compound into another. For example, 1-butene (C4H8) is converted to butane (C4H10) by addition of H2. Use the bond dissociation enthalpies in Table 8.8 to estimate the enthalpy change for this hydrogenation reaction.arrow_forwardUsing the bond dissociation enthalpies in Table 8.8, estimate the enthalpy of combustion of gaseous methane, CH4, to give water vapor and carbon dioxide gas.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
- Methanol can be made by partial oxidation of methane using O2 in the presence of a catalyst: 2 CH4(g) + O2(g) 2 CH3OH() Use bond dissociation enthalpies to estimate the enthalpy change for this reaction. Compare the value obtained to the value calculated using standard enthalpies of formation.arrow_forwardBond 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_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
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