
Concept explainers
The 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 S—F bond.
b. Compare your calculated value to the value given in Table 3-3. What conclusions can you draw?
c. Why are the ΔH°f values for S(g) and F(g) not equal to zero, since sulfur and fluorine are elements?
(a)

Interpretation:
The S- F bond energy should be calculated and standard enthalpies of formation values of S(g) and F(g) should be explained.
Hess's Law:
Standard enthalpy of formation:
- The change in enthalpy that associate with the formation of one mole of a product from its pure elements, with all substances in its standard states is called as a standard enthalpy of formation.
- Formula:
ΔHf = ∑npΔH°f(products)-∑nrΔH°f(reactants)......(1)
- Internal energy change of a reaction is given as,
-
Internal energy change ΔE= Bond broken energy - Bond formation energy
ΔE = ∑Dbroken-∑Dformed......(2)
- The internal energy change is equal to enthalpy change in the gas phase reactions.
- The dissociation bond energy is equal to enthalpy change in the gas phase reactions
Answer to Problem 136CP
- The SF bond energy in SF6 is 327 kJ/mol.
- The SF bond energy in SF4 342.5 kJ
Explanation of Solution
Record data from given:
Standard enthalpies of formation S(g) is +278.8 kJ/molStandard enthalpies of formation F(g) is +79.0 kJ/molStandard enthalpies of formation SF4(g) is -775 kJ/molStandard enthalpies of formationSF6(g) is +1209 kJ/mol
To calculate the SF bond energy in SF4 .
SF4 dissociation reaction : SF4(g)→S(g)+4F(g) ΔH°= 278.8+4(79.0)-(775) ΔH°= 1370 kJ DSF= ΔH°Number of S-F bondThis enthalpy change is equal to 4 ×(dissociation energy SF bond). DSF= 1370 kJ4 =342.5 kJ/mol
- The given standard enthalpies of formation values are plugging in to above equation 1to given the enthalpy change of the reactions.
- This enthalpy change divide by 4 to give SF bond energy in SF4 .
- The SF bond energy in SF4 342.5 kJ.
To calculate the SF bond energy in SF6 .
SF4 dissociation reaction : SF6(g)→S(g)+6F(g) ΔH°= 278.8+6(79.0)-(1209) ΔH°= 1962 kJ DSF= ΔH°Number of S-F bondThis enthalpy change is equal to 6 ×(dissociation energy SF bond). DSF= 1962kJ6 =327.0 kJ/mol
(b)

Interpretation:
The S- F bond energy should be calculated and standard enthalpies of formation values of S(g) and F(g) should be explained.
Hess's Law:
Standard enthalpy of formation:
- The change in enthalpy that associate with the formation of one mole of a product from its pure elements, with all substances in its standard states is called as a standard enthalpy of formation.
- Formula:
ΔHf = ∑npΔH°f(products)-∑nrΔH°f(reactants)......(1)
- Internal energy change of a reaction is given as,
-
Internal energy change ΔE= Bond broken energy - Bond formation energy
ΔE = ∑Dbroken-∑Dformed......(2)
- The internal energy change is equal to enthalpy change in the gas phase reactions.
- The dissociation bond energy is equal to enthalpy change in the gas phase reactions
Answer to Problem 136CP
- The SF bond energy in table is SF6 .
Explanation of Solution
- The standard enthalpy of formation values are plugging in to equation (1) to get enthalpy change of the reaction.
- This enthalpy change divide by 6 to give SF bond energy in SF6 .
- The SF bond energy in SF6 is 327 kJ/mol.
(c)

Interpretation:
The S- F bond energy should be calculated and standard enthalpies of formation values of S(g) and F(g) should be explained.
Hess's Law:
Standard enthalpy of formation:
- The change in enthalpy that associate with the formation of one mole of a product from its pure elements, with all substances in its standard states is called as a standard enthalpy of formation.
- Formula:
ΔHf = ∑npΔH°f(products)-∑nrΔH°f(reactants)......(1)
- Internal energy change of a reaction is given as,
-
Internal energy change ΔE= Bond broken energy - Bond formation energy
ΔE = ∑Dbroken-∑Dformed......(2)
- The internal energy change is equal to enthalpy change in the gas phase reactions.
- The dissociation bond energy is equal to enthalpy change in the gas phase reactions
Answer to Problem 136CP
- The standard state of Sulfur is and Fluorine are S8(g) and F2(g) states so the given states are S(g) and F(g) not stable so standard enthalpies of formation values are all so not zero.
Explanation of Solution
- In the standard data table the given SF bond energy is 327 kJ/mol and the calculated bond energies are compared to standard data, the SF bond energy 327 kJ/mol is based on the SF6 .
- The standard state of Sulfur is and Fluorine are S8(g) and F2(g) states so the given states are S(g) and F(g) not stable so standard enthalpies of formation values are all so not zero..
Want to see more full solutions like this?
Chapter 6 Solutions
Bundle: Chemistry, 10th + Laboratory Handbook for General Chemistry, 3rd + Student Resource Center Printed Access Card + Student Solutions Manual for ... Access Card for Zumdahl/Zumdahl/DeCoste
- Draw the major product of this reaction. Ignore inorganic byproducts and the amine side product. 'N' 1. NaOH, heat 2. Neutralizing work-up Select to Drawarrow_forwardSubmit Problem 3 of 10 Draw the major product of this reaction. Ignore inorganic byproducts and the amine side product. O 'N' NH 1. NaOH, heat 2. Neutralizing work-up Select to Drawarrow_forwardb) Certain cyclic compounds are known to be conformationally similar to carbohydrates, although they are not themselves carbohydrates. One example is Compound C shown below, which could be imagined as adopting four possible conformations. In reality, however, only one of these is particularly stable. Circle the conformation you expect to be the most stable, and provide an explanation to justify your choice. For your explanation to be both convincing and correct, it must contain not only words, but also "cartoon" orbital drawings contrasting the four structures. Compound C Possible conformations (circle one): Детarrow_forward
- Lab Data The distance entered is out of the expected range. Check your calculations and conversion factors. Verify your distance. Will the gas cloud be closer to the cotton ball with HCI or NH3? Did you report your data to the correct number of significant figures? - X Experimental Set-up HCI-NH3 NH3-HCI Longer Tube Time elapsed (min) 5 (exact) 5 (exact) Distance between cotton balls (cm) 24.30 24.40 Distance to cloud (cm) 9.70 14.16 Distance traveled by HCI (cm) 9.70 9.80 Distance traveled by NH3 (cm) 14.60 14.50 Diffusion rate of HCI (cm/hr) 116 118 Diffusion rate of NH3 (cm/hr) 175.2 175.2 How to measure distance and calculate ratearrow_forwardFor the titration of a divalent metal ion (M2+) with EDTA, the stoichiometry of the reaction is typically: 1:1 (one mole of EDTA per mole of metal ion) 2:1 (two moles of EDTA per mole of metal ion) 1:2 (one mole of EDTA per two moles of metal ion) None of the abovearrow_forwardPlease help me solve this reaction.arrow_forward
- Indicate the products obtained by mixing 2,2-dimethylpropanal with acetaldehyde and sodium ethoxide in ethanol.arrow_forwardSynthesize 2-Ethyl-3-methyloxirane from dimethyl(propyl)sulfonium iodide using the necessary organic or inorganic reagents. Draw the structures of the compounds.arrow_forwardSynthesize 2-Hydroxy-2-phenylacetonitrile from phenylmethanol using the necessary organic or inorganic reagents. Draw the structures of the compounds.arrow_forward
- Synthesize N-Methylcyclohexylamine from cyclohexanol using the necessary organic or inorganic reagents. Draw the structures of the compounds.arrow_forwardSynthesize N-Methylcyclohexylamine from cyclohexanol using the necessary organic or inorganic reagents. Draw the structures of the compounds.arrow_forwardIf possible, please provide the formula of the compound 3,3-dimethylbut-2-enal.arrow_forward
- Chemistry: An Atoms First ApproachChemistryISBN:9781305079243Author:Steven S. Zumdahl, Susan A. ZumdahlPublisher:Cengage LearningChemistryChemistryISBN:9781305957404Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCostePublisher:Cengage Learning
- Introductory Chemistry: A FoundationChemistryISBN:9781337399425Author:Steven S. Zumdahl, Donald J. DeCostePublisher:Cengage LearningChemistry & Chemical ReactivityChemistryISBN:9781337399074Author:John C. Kotz, Paul M. Treichel, John Townsend, David TreichelPublisher:Cengage LearningChemistry & Chemical ReactivityChemistryISBN:9781133949640Author:John C. Kotz, Paul M. Treichel, John Townsend, David TreichelPublisher:Cengage Learning





