Connect for Chemistry
13th Edition
ISBN: 9781260161854
Author: Raymond Chang, Jason Overby
Publisher: Mcgraw-hill Higher Education (us)
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Textbook Question
Chapter 9, Problem 9.72QP
Explain why the bond enthalpy of a molecule is usually defined in terms of a gas-phase reaction. Why are bond-breaking processes always endothermic and bond-forming processes always exothermic?
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Students have asked these similar questions
In chemical reactions, heat is converted into chemical energy (the potential energy stored
in chemical bonds) or vice versa. Bond energy is the energy required to break one mole of
the bond in the gas phase. Since it takes energy to break a bond, bond energies are
always positive. Conversely, energy is released when bonds are formed. Thus, the
enthalpy change for a reaction can be approximated from
Part A
Calculate the bond energy per mole for breaking all the bonds in methane, CH4.
ΔΗ
Σ(ΔΗ breaking) + Σ(ΔΗ forming)
Express your answer to four significant figures and include the appropriate units.
where H represents bond energies for the breaking (positive bond energy) or forming
(negative bond energy) of a bond and Hrxn represents the overall enthalpy for the
• View Available Hint(s)
reaction.
Use the table to answer questions about bond energies.
HẢ
Bond energy
Bond
(kJ/mol )
Value
Units
AHCH, =
C-C
347
C=C
611
Submit
Сн
414
C-O
360
Part B
C=OinCO2
799
O-0
142
Calculate the bond…
8) In an exothermic reaction, the enthalpy of the reaction can be calculated by
a. Subtracting the sum of all the bond energies of the
products from the sum of all the bond energies of the
reactants.
b. Subtracting the sum of all the bond energies of the reactants
from the sum of all the bond energies of the products
c. Finding the sum of the enthalpies of formation of all the
products and reactants together d. All of the above
Explain the difference between endothermic reactions and exothermic reactions with respect to the bond energies of the bonds broken and formed.
Chapter 9 Solutions
Connect for Chemistry
Ch. 9.1 - Prob. 1RCFCh. 9.1 - Using only the periodic table, determine the Lewis...Ch. 9.1 - To what group on the periodic table does element X...Ch. 9.2 - Use Lewis dot symbols to represent the formation...Ch. 9.2 - Use Lewis dot symbols to represent the formation...Ch. 9.3 - Which of the following compounds has a larger...Ch. 9.3 - Arrange the compounds NaF, MgO, and AIN in order...Ch. 9.4 - Why is it not possible for hydrogen to form double...Ch. 9.4 - Arrange the bonds NN, NN, and NN in order of...Ch. 9.5 - Which of the following bonds is covalent, which is...
Ch. 9.5 - Rank the bonds BH, CCl, and PP in order of...Ch. 9.5 - Classify the following bonds as covalent, polar...Ch. 9.5 - Identify the electrostatic potential maps shown...Ch. 9.6 - Write the Lewis structure for carbon disulfide...Ch. 9.6 - Write the Lewis structure for formic acid (HCOOH).Ch. 9.6 - Write the Lewis structure for the nitrite ion...Ch. 9.6 - Write the Lewis structure for PCl3.Ch. 9.6 - Write the Lewis structure for CN.Ch. 9.6 - The molecular model shown here represents guanine,...Ch. 9.7 - Write formal charges for the nitrite ion (NO2).Ch. 9.7 - Draw the most reasonable Lewis structure of a...Ch. 9.7 - Write the formal charges on H, C, and N,...Ch. 9.7 - Write the formal charges on O and Cl,...Ch. 9.7 - Consider three possible atomic arrangements for...Ch. 9.8 - Draw three resonance structures for the...Ch. 9.8 - Draw three resonance structures for SO2.Ch. 9.8 - The molecular model shown here represents...Ch. 9.9 - Prob. 9PECh. 9.9 - Prob. 10PECh. 9.9 - Prob. 11PECh. 9.9 - Write the Lewis structure of sulfur tetrafluoride...Ch. 9.9 - Both boron and aluminum tend to form compounds in...Ch. 9.9 - Draw a Lewis structure for IF5.Ch. 9.9 - Prob. 3RCFCh. 9.10 - Calculate the enthalpy of the reaction...Ch. 9.10 - For the reaction H2(g)+C2H4(g)C2H6(g) (a) Estimate...Ch. 9.10 - Why does Hrxn calculated using bond enthalpies not...Ch. 9.10 - Using bond enthalpy values, predict the enthalpy...Ch. 9 - What is a Lewis dot symbol? To what elements does...Ch. 9 - Use the second member of each group from Group 1A...Ch. 9 - Prob. 9.3QPCh. 9 - Write Lewis dot symbols for the following ions:...Ch. 9 - Write Lewis dot symbols for the following atoms...Ch. 9 - Explain what an ionic bond is.Ch. 9 - Prob. 9.7QPCh. 9 - Name five metals and five nonmetals that are very...Ch. 9 - Name one ionic compound that contains only...Ch. 9 - Name one ionic compound that contains a polyatomic...Ch. 9 - Prob. 9.11QPCh. 9 - In which of the following states would NaCl be...Ch. 9 - Prob. 9.14QPCh. 9 - An ionic bond is formed between a cation A+ and an...Ch. 9 - Prob. 9.16QPCh. 9 - Use Lewis dot symbols to show the transfer of...Ch. 9 - Prob. 9.18QPCh. 9 - For each of the following pairs of elements, state...Ch. 9 - Prob. 9.20QPCh. 9 - What is lattice energy and what role does it play...Ch. 9 - Explain how the lattice energy of an ionic...Ch. 9 - Specify which compound in the following pairs of...Ch. 9 - Compare the stability (in the solid state) of the...Ch. 9 - Use the Born-Haber cycle outlined in Section 9.3...Ch. 9 - Calculate the lattice energy of calcium chloride...Ch. 9 - What is Lewiss contribution to our understanding...Ch. 9 - Use an example to illustrate each of the following...Ch. 9 - What is the difference between a Lewis dot symbol...Ch. 9 - How many lone pairs are on the underlined atoms in...Ch. 9 - Compare single, double, and triple bonds in a...Ch. 9 - Compare the properties of ionic compounds and...Ch. 9 - Define electronegativity, and explain the...Ch. 9 - List the following bonds in order of increasing...Ch. 9 - Arrange the following bonds in order of increasing...Ch. 9 - Four atoms are arbitrarily labeled D, E, F, and G....Ch. 9 - List the following bonds in order of increasing...Ch. 9 - Classify the following bonds as ionic, polar...Ch. 9 - Classify the following bonds as ionic, polar...Ch. 9 - Summarize the essential features of the Lewis...Ch. 9 - The octet rule applies mainly to the second-period...Ch. 9 - Write Lewis structures for the following molecules...Ch. 9 - Write Lewis structures for the following molecules...Ch. 9 - Write Lewis structures for the following...Ch. 9 - Write Lewis structures for the following...Ch. 9 - The following Lewis structures for (a) HCN, (b)...Ch. 9 - The skeletal structure of acetic acid shown here...Ch. 9 - Prob. 9.49QPCh. 9 - Do formal charges represent actual separation of...Ch. 9 - Write Lewis structures for the following ions: (a)...Ch. 9 - Write Lewis structures for the following ions: (a)...Ch. 9 - Define bond length, resonance, and resonance...Ch. 9 - Is it possible to trap a resonance structure of a...Ch. 9 - Write Lewis structures for the following species,...Ch. 9 - Draw three resonance structures for the chlorate...Ch. 9 - Write three resonance structures for hydrazoic...Ch. 9 - Draw two resonance structures for diazomethane,...Ch. 9 - Draw three resonance structures for the molecule...Ch. 9 - Draw three reasonable resonance structures for the...Ch. 9 - Why does the octet rule not hold for many...Ch. 9 - Give three examples of compounds that do not...Ch. 9 - Because fluorine has seven valence electrons...Ch. 9 - What is a coordinate covalent bond? Is it...Ch. 9 - Prob. 9.65QPCh. 9 - In the vapor phase, beryllium chloride consists of...Ch. 9 - Of the noble gases, only Kr, Xe, and Rn are known...Ch. 9 - Write a Lewis structure for SbCl5. Does this...Ch. 9 - Prob. 9.69QPCh. 9 - Write Lewis structures for the reaction...Ch. 9 - What is bond enthalpy? Bond enthalpies of...Ch. 9 - Explain why the bond enthalpy of a molecule is...Ch. 9 - From the following data, calculate the average...Ch. 9 - For the reaction O(g)+O2(g)O3(g)H=107.2kJ/mol...Ch. 9 - The bond enthalpy of F2(g) is 156.9 kJ/mol....Ch. 9 - For the reaction 2C2H6(g)+7O2(g)4CO2(g)+6H2O(g)...Ch. 9 - Prob. 9.77QPCh. 9 - Which of the following are ionic compounds? Which...Ch. 9 - Prob. 9.79QPCh. 9 - Use ionization energy (see Table 8.2) and electron...Ch. 9 - Prob. 9.82QPCh. 9 - Prob. 9.83QPCh. 9 - Write three reasonable resonance structures for...Ch. 9 - Prob. 9.85QPCh. 9 - Give an example of an ion or molecule containing...Ch. 9 - Draw four reasonable resonance structures for the...Ch. 9 - Prob. 9.88QPCh. 9 - Draw reasonable resonance structures for the...Ch. 9 - Are the following statements true or false? (a)...Ch. 9 - Prob. 9.91QPCh. 9 - Using the following information and the fact that...Ch. 9 - Prob. 9.93QPCh. 9 - Which of the following molecules has the shortest...Ch. 9 - Most organic acids can be represented as RCOOH,...Ch. 9 - Which of the following species are isoelectronic:...Ch. 9 - The following species have been detected in...Ch. 9 - The amide ion, NH2, is a Brnsted base. Represent...Ch. 9 - Draw Lewis structures for the following organic...Ch. 9 - The triiodide ion (I3) in which the I atoms are...Ch. 9 - Compare the bond enthalpy of F2 with the energy...Ch. 9 - Methyl isocyanate (CH3NCO) is used to make certain...Ch. 9 - Prob. 9.103QPCh. 9 - Prob. 9.104QPCh. 9 - Prob. 9.105QPCh. 9 - Draw Lewis structures for the following...Ch. 9 - Prob. 9.107QPCh. 9 - Prob. 9.108QPCh. 9 - Draw Lewis structures for the following organic...Ch. 9 - Write Lewis structures for the following four...Ch. 9 - Prob. 9.111QPCh. 9 - Prob. 9.112QPCh. 9 - Write three resonance structures for (a) the...Ch. 9 - (a) From the following data calculate the bond...Ch. 9 - Prob. 9.115QPCh. 9 - What are the other two reasons for choosing (b) in...Ch. 9 - Prob. 9.117QPCh. 9 - The NO bond distance in nitric oxide is 115 pm,...Ch. 9 - Prob. 9.119QPCh. 9 - Prob. 9.120QPCh. 9 - Prob. 9.121QPCh. 9 - Prob. 9.122QPCh. 9 - Draw a Lewis structure for nitrogen pentoxide...Ch. 9 - In the gas phase, aluminum chloride exists as a...Ch. 9 - The hydroxyl radical (OH) plays an important role...Ch. 9 - Experiments show that it takes 1656 kJ/mol to...Ch. 9 - Calculate Hrxn at 25C of the reaction between...Ch. 9 - Calculate Hrxn at 25C of the reaction between...Ch. 9 - Draw three resonance structures of sulfur dioxide...Ch. 9 - Vinyl chloride (C2H3Cl) differs from ethylene...Ch. 9 - Prob. 9.131QPCh. 9 - The American chemist Robert S. Mulliken suggested...Ch. 9 - Prob. 9.133QPCh. 9 - A student in your class claims that magnesium...Ch. 9 - Shown here is a skeletal structure of borazine...Ch. 9 - Calculate the wavelength of light needed to carry...Ch. 9 - Prob. 9.137QPCh. 9 - From the lattice energy of KCl in Table 9.1 and...Ch. 9 - The species H3+ is the simplest polyatomic ion....Ch. 9 - The bond enthalpy of the CN bond in the amide...Ch. 9 - In 1999 an unusual cation containing only nitrogen...Ch. 9 - Nitroglycerin, one of the most commonly used...Ch. 9 - Give a brief description of the medical uses of...Ch. 9 - Prob. 9.144QPCh. 9 - The isolated O2 ion is unstable so it is not...Ch. 9 - When irradiated with light of wavelength 471.7 nm,...Ch. 9 - Recall from Chapter 8 that the product of the...Ch. 9 - The reaction between fluorine (F2) with ethane...Ch. 9 - A new allotrope of oxygen, O4, has been reported....Ch. 9 - Because bond formation is exothermic, when two...Ch. 9 - Estimate Hf for sodium astatide (NaAt) according...
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- 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_forwardhat is the enthalpy change for a process? Is enthalpy a state function? In what experimental apparatus are enthalpy changes measured?arrow_forwardWrite all resonance structures of chlorobenzene, C6H5Cl, a molecule with the same cyclic structure as benzene. In all structures, keep the CCl bond as a single bond. Which resonance structures are the most important?arrow_forward
- Using the standard enthalpy of formation data in Appendix G, show how the standard enthalpy of formation of HCl(g) can be used to determine the bond energy.arrow_forwardWhich statement(s) is/are true about bond enthalpy? (a) The bond energy for a triple bond between A and B is three times that of a single bond between A and B. (b) H for the breaking of a bond is always a negative number. (c) Energy is required to make a bond. (d) Bond enthalpy is defined only for bonds broken or formed in the gaseous state. (e) The presence of bonds does not influence the geometry of a molecule. However, the presence of bonds affects the value of the bond enthalpy between two atoms.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
- Compare 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_forwardExplain the decomposition of nitroglycerin in terms of relative bond enthalpies.arrow_forwardWrite the Lewis structure for nitrosyl fluoride, FNO. Using only a periodic table, identify (a) which is the longer bond. (b) which is the stronger bond. (c) which is the more polar bond.arrow_forward
- Methylcyanoacrylate is the active ingredient in super glues. Its Lewis structure is In this molecule, which is the (a) weakest carbon-containing bond? (b) strongest carbon-containing bond? (c) most polar bond?arrow_forwardDraw 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_forwardUse bond energies to determine ΔHrxn for the reaction between ethanol and hydrogen chloride. CH3CH2OH(g)+HCl(g)→CH3CH2Cl(g)+H2O(g) Average Bond Energies Bond Bond Energy (kJ/mol) H−C 414 H−O 464 H−F 565 H−Cl 431 H−Br 364 C−Cl 339 C−O 360 Cl−F 253 Cl−Cl 243 Br−Cl 218arrow_forward
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