For the reaction A(g) + 2 B(g) ↔ C(g) the initial partial pressures of gases A, B, and C are all 0.109 atm. Once equilibrium has been established, it is found that PC = 0.047 atm. What is ΔG° for this reaction (in kJ/mol) at 25°C?

Respuesta :

Explanation:

As the given reaction is as follows.

             [tex]A(g) + 2B(g) \leftrightarrow C(g)[/tex]

The given data is as follows.

Initially,    [tex]P_{A}[/tex] = 0.109 atm,     [tex]P_{B}[/tex] = 0.109 atm,

                [tex]P_{C}[/tex] = 0.109 atm

And, at equilibrium

        [tex]P_{C}[/tex] = 0.047 atm

Therefore, change in [tex]P_{C}[/tex] will be calculated as follows.

                    0.109 - 0.047

                 = 0.062 atm

Hence, [tex]P_{A}[/tex] = (0.109 + 0.062) atm = 0.171 atm

[tex]P_{B}[/tex] = [tex][0.109 + (2 \times 0.062)][/tex] atm

                        = 0.233 atm

Now, calculate the value of [tex]K_{p}[/tex] as follows.

         [tex]K_{p} = \frac{P_{C}}{(P_{A})(P_{B})^{2}}[/tex]

                    = [tex]\frac{0.047}{(0.171) \times (0.233)^{2}}[/tex]

                    = 5.06

Also, we known that [tex]\Delta G^{o} = -RT lnK_{p}[/tex]

Hence, calculate the value of [tex]\Delta G^{o}[/tex] as follows.

        [tex]\Delta G^{o} = -RT lnK_{p}[/tex]

                      = [tex]-8.314 J/mol K \times 298 K \times ln 5.06[/tex]

                       = [tex]-8.314 J/mol K \times 298 K \times 1.62[/tex]

                      = -4017.05 J/mol

or,                   = -4.017 kJ/mol              (as 1 kJ = 1000 J)

Thus, we can conclude that the value of [tex]\Delta G^{o}[/tex] for the given reaction is -4.017 kJ/mol.

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