Concept explainers
(a)
Interpretation:
The average
Concept Introduction:
Bond energy means the amount of energy need to break a mole of molecules into its constituent atoms.
The expression for the enthalpy change is:
(a)
Explanation of Solution
Given,
The average
Therefore, the average bond energy is
(b)
Interpretation:
(b)
Explanation of Solution
There are four
(c)
Interpretation:
The average
(c)
Explanation of Solution
To break the
Figure 1
Average Bond Energy in gas-phase
Given,
Therefore, the average bond energy is
Average Bond Energy in gas-phase
Given,
Therefore, the average bond energy is
Average Bond Energy in gas-phase
Given,
Therefore, the average bond energy is
It is easier to break a bond in an unstable molecule than in a stable molecule.
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Chapter 6 Solutions
Chemistry: The Molecular Science
- Enthalpy changes for the following reactions can be determined experimentally: N2(g) + 3 H2(g) 2 NH3(g) rH = 91.8 kJ/mol-rxn 4 NH3(g) + 5 O2(g) 4 NO(g) + 6 H2O(g) rH = 906.2 kJ/mol-rxn H2(g) + O2(g) H2O(g) rH = 241.8 kl/mol-rxn Use these values to determine the enthalpy change for the formation of NO(g) from the elements (an enthalpy change that cannot be measured directly because the reaction is reactant-favored). N2(g) + O2(g) NO(g) rH = ?arrow_forward9.99 The chemical reaction BBr3(g)+BCl3(g)BBr2Cl(g)+BCl2Br(g) , has an enthalpy change very close to zero. Using Lewis structures of the molecules, all of which have a central boron atom, provide a molecular-level description of why H for this reaction might be very small.arrow_forwardThe bond energy for a CH bond is about 413 kJ/mol in CH4 but 380 kJ/mol in CHBr3. Although these values are relatively close in magnitude, they are different. Explain why they are different. Does the fact that the bond energy is lower in CHBr3, make any sense? Why?arrow_forward
- hat is the enthalpy change for a process? Is enthalpy a state function? In what experimental apparatus are enthalpy changes measured?arrow_forwardGiven 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_forward
- 9.41 Under what conditions does the enthalpy change equal the heat of a process?arrow_forwardYou discover that you cannot carry out a particular reaction for which you would like the enthalpy change. Does this mean that you will be unable to obtain this enthalpy change? Explain.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 3-3. What conclusions can you draw? c. Why are the Hf values for S(g) and F(g) not equal to zero, since sulfur and fluorine are elements?arrow_forward
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