Concept explainers
Values of measured bond energies may vary greatly depending on the molecule studied. Consider the following reactions:
Rationalize the difference in the values of ∆E for these reactions, even though each reaction appears to involve only the breaking of one N—Cl bond. (Hint: Consider the bond order of the NO bond in ONCl and in NO.)
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Chapter 9 Solutions
Chemistry
- Using 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_forwardHydrogenation 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_forwardThree resonance forms can be drawn for the molecule N2O. Which resonance form is likely to more closely resemble the structure of this molecule? (a) (b) (c)arrow_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_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_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
- Draw a Lewis structure for each of the following molecules or ions. (a) CS2 (b) BF4 (c) HNO2 (where the bonding is in the order HONO) (d) OSCl2 (where S is the central atom)arrow_forwardEthanol can be made by the reaction of ethylene and water: H2C=CH2(g) + H2O(g) CH3CH2OH(g) Use bond dissociation enthalpies to estimate the enthalpy change in this reaction. Compare the value obtained to the value calculated from enthalpies of formation.arrow_forwardThe molecular structure shown is of one form of glucose, C6H12O6 Glucose can be oxidized to carbon dioxide and water according to the equation C6H12O6(S) + 6 O2(g)6 CO2(g) + 6 H2O(g) (a) Using the method described in Section 6-6a for estimating enthalpy changes from bond energies, estimate rH for the oxidation of this form of glucose. Make a list of all bonds broken and all bonds formed in this process. (b) Compare your result with the experimental value of 2816 kJ/mol for combustion of glucose. Why might there be a difference between this value and the one you calculated in part (a)?arrow_forward
- An important observation supporting the concept of resonance in the localized electron model was that there are only three different structures of dichlorobenzene (C6H4C10). How does this fact support the concept of resonance (see Exercise 89)?arrow_forwardhat is the enthalpy change for a process? Is enthalpy a state function? In what experimental apparatus are enthalpy changes measured?arrow_forward
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