Question

Question: Use bond energies (Table 13.6), values of electron affinities (Table 12.8), and the ionization energy of hydrogen (1312 kJ/mol) to estimate𝛥H for each of the following reactions.

a. HF_(g)H⁺_(g) + F^-_(g)

b. HCl_(g)H⁺_(g)⁺ Cl^-_(g)

c. HI_(g)H⁺_(g) + I^-_(g)

d. H₂O_(g)H⁺_(g) + OH^-_(g)

(Electron affinity of OH_(g) -180. kJ/mol.)

Short answer

The ionization energy of Hydrogen is 1312 KJ/mol.

The electron affinity of OH_(g) -180 kJ/mol.

Required data for Bond energy and electron affinities are given in table 13.6 & table 12.8.

Step-by-step solution

Step 1:Describing the reactions, ionization energy, and electron affinity

In the gaseous state, the hydrogen atom is ionized where it loses an electron from valence orbit. The ionized form is a proton (H⁺).

H_(g)H⁺_(g) + e^-_{(g)$\mathbf{\left(}\mathbf{1}\mathbf{\right)}$}

The energy required to ionize the atom is the ionization energy. Therefore, the required ionization energy is 1312 KJ/mol.

Also, for F, Cl and Br atoms tend to gain electrons which further form F^-, Cl^- and Br^- respectively.

Hence,

F + e^- F^{-$\left(2\right)$}

Cl + e^- Cl^-

Br + e^-Br^-

OH + e^-OH^-

Step 2:Summing up the above reactions to get required reactions

By adding above reactions respectively with (1) will get reactions

HF_(g) H⁺_(g) + F^-_(g)

HCl_(g)H⁺_(g)⁺ Cl^-_(g)

HI_(g) H⁺_(g) + I^-_(g)

H₂O_(g)H⁺_(g) + OH^-_(g)

Determining 𝛥H for the above reactions

The enthalpy of reaction (𝛥H)is

𝛥H =𝞢𝛥H_(products) -𝞢𝛥H_(reactants)

Here

𝛥H = [𝛥H(I.E of H) +𝛥H(E.A of X)] - [𝛥H_(HX)]

Therefore,

For (6)

𝛥H = [𝛥H (I.E of H) +𝛥H (E.A of F)] - [𝛥H_(HF)]

= {1312) + (-327.8)}– {- 565}

= 1549.2 KJ/mol

For (7)

𝛥H = [𝛥H (I.E of H) +𝛥H (E.A of Cl)] - [𝛥H_(HCl)]

={1312 + (-348.7)} – {-427}

= 1390.3 KJ/mol

For (8)

𝛥H = {𝛥H (I.E of H) +𝛥H (E.A of Br)] - {𝛥H_(HBr)]

= {1312 + (-324.5)} - {-363}

= 1350.5 KJ/mol

For (9)

𝛥H = {𝛥H (I.E of H) +𝛥H (E.A of OH)] - {𝛥H_(HOH)]

= (1312 + (-180)) – (-286)

=1418 KJ/mol

Determining the final values

The enthalpy of reaction(𝛥H) is1549.2, 1390.3, 1350.5, and1418 KJ/mol.