Carbon disulfide, CS2, has the Lewis structure S̈=C=S̈, and for C S2(g), ΔHf^∘=+115.3 kJ mol^-

step 1 To estimate the C double bond S bond energy, knowing the delta H of formation of carbon disulfid

Carbon disulfide, CS2, has the Lewis structure S̈=C=S̈, and...

Carbon disulfide, $\mathrm{CS}_{2}$, has the Lewis structure $\ddot{S}=C=\ddot{S},$ and for $C S_{2}(g), \Delta H_{\mathrm{f}}^{\circ}=+115.3 \mathrm{~kJ} \mathrm{~mol}^{-1}$
Use the data in Table 18.3 to calculate the average $\mathrm{C}=\mathrm{S}$ bond energy in this molecule.

Key Concepts

Enthalpy of Formation

Enthalpy of formation (?Hf°) is the change in enthalpy when one mole of a compound is formed from its elements in their standard states. This fundamental thermochemical quantity provides a basis for calculating reaction enthalpies using formation data and is often used in bond energy calculations via thermochemical cycles.

Hess's Law

Hess's Law states that the total enthalpy change for a reaction is the same regardless of the pathway taken, provided the initial and final conditions are identical. This principle enables the use of known enthalpy changes, such as standard heats of formation and bond energies, to calculate unknown energy changes in chemical reactions through the construction of thermochemical cycles.

Bond Energy

Bond energy represents the amount of energy required to break a chemical bond in a molecule in the gas phase. It is a useful concept for understanding molecular stability, reactivity, and thermochemical calculations, as it allows chemists to quantify the strength of individual bonds within a molecule.

Average Bond Energy

Average bond energy is calculated when bonds are identical in a molecule, and refers to the mean energy required to break each bond. In molecules where the same type of bond repeats, such as in a symmetric molecule, the total energy to break all bonds is divided equally among them, resulting in the average bond energy for one bond.

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