Use bond energies (Table 8.4), values of electron affinities...

Use bond energies (Table 8.4), values of electron affinities (Table 7.7), and the ionization energy of hydrogen $(1312 \mathrm{~kJ} / \mathrm{mol}$ ) to estimate $\Delta H$ for each of the following reactions. a. $\mathrm{HF}(\mathrm{g}) \rightarrow \mathrm{H}^{+}(\mathrm{g})+\mathrm{F}^{-}(g)$ b. $\mathrm{HCl}(g) \rightarrow \mathrm{H}^{+}(g)+\mathrm{Cl}^{-}(g)$ c. $\mathrm{HI}(g) \rightarrow \mathrm{H}^{+}(g)+\mathrm{I}^{-}(g)$ d. $\mathrm{H}_{2} \mathrm{O}(g) \rightarrow \mathrm{H}^{+}(g)+\mathrm{OH}^{-}(g)$ (Electron affinity of $\mathrm{OH}(g)=-180 . \mathrm{kJ} / \mathrm{mol}$.)

Use bond energies (Table 8.4), values of electron affinities (Table 7.7), and the ionization energy of hydrogen $(1312 \mathrm{~kJ} / \mathrm{mol}$ ) to estimate $\Delta H$ for each of the following reactions.
a. $\mathrm{HF}(\mathrm{g}) \rightarrow \mathrm{H}^{+}(\mathrm{g})+\mathrm{F}^{-}(g)$
b. $\mathrm{HCl}(g) \rightarrow \mathrm{H}^{+}(g)+\mathrm{Cl}^{-}(g)$
c. $\mathrm{HI}(g) \rightarrow \mathrm{H}^{+}(g)+\mathrm{I}^{-}(g)$
d. $\mathrm{H}_{2} \mathrm{O}(g) \rightarrow \mathrm{H}^{+}(g)+\mathrm{OH}^{-}(g)$
(Electron affinity of $\mathrm{OH}(g)=-180 . \mathrm{kJ} / \mathrm{mol}$.)

Key Concepts

Thermochemical Cycles

Thermochemical cycles are a method to determine reaction enthalpies by constructing a series of steps that add up to the overall reaction. These cycles use bond energies, ionization energies, and electron affinities, leveraging the principle of Hess's law to compute the net enthalpic change.

Hess's Law

Hess's law states that the total enthalpy change for a reaction is independent of the pathway taken. This principle allows one to calculate the overall reaction enthalpy by summing energy changes from individual steps, such as bond breaking, electron removal, and electron gain.

Ionization Energy

Ionization energy is the energy needed to remove an electron from a neutral atom or molecule in the gas phase. This concept is essential for determining the energy required to form cations and is a critical parameter in chemical energetics.

Electron Affinity

Electron affinity is the energy change that occurs when an electron is added to a neutral atom or molecule to form an anion. It reflects an atom’s tendency to accept an electron, influencing the overall energy balance in reactions involving ion formation.

Bond Energy

Bond energy is the measure of the strength of a chemical bond, defined as the amount of energy required to break one mole of bonds in gaseous molecules. It is a key concept in understanding the energy changes during bond breaking and formation in chemical reactions.

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