Concept explainers
Interpretation:
The
Concept introduction:
Bond enthalpy:
The measure of stability of molecule is bond enthalpy. The change in enthalpy is related in breaking a specific bond of 1 mole of gaseous molecule. In solids and liquids bond enthalpies are affected by neighboring molecules. There is possibility to predict the enthalpy of reaction using the average bond enthalpies. Energy is always needed for the breaking of
The enthalpy of reaction in gas phase is given by,
To estimate the
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General Chemistry - Standalone book (MindTap Course List)
- The 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_forwardUsing a table of average bond enthalpies. Table 6.2 ( Sec. 6-6b), estimate the enthalpy change for the industrial synthesis of methanol by the catalyzed reaction of carbon monoxide with hydrogen.arrow_forwardGiven the following data: NO2(g) NO(g) + O(g)H = 233 kJ 2O3(g) 3O2(g)H = 427 kJ NO(g) + O3(g) NO2(g) + O2(g)H = 199 kJ Calculate the bond energy for the O2 bond, that is, calculate H for: O2(g) 2O(g)H = ?arrow_forward
- 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_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_forwardhat is the enthalpy change for a process? Is enthalpy a state function? In what experimental apparatus are enthalpy changes measured?arrow_forward
- Is the following reaction the appropriate one to use in determining the enthalpy of formation of methane, CH4(g)? Why or why not? C(g)+4H(g)CH4(g)arrow_forwardEnthalpy 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_forwardThe enthalpy change for the following reaction is 393.5 kJ. C(s,graphite)+O2(g)CO2(g) (a) Is energy released from or absorbed by the system in this reaction? (b) What quantities of reactants and products are assumed? (c) Predict the enthalpy change observed when 3.00 g carbon burns in an excess of oxygen.arrow_forward
- Estimate 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_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
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