In the Mond process for the purification of nickel, carbon monoxide is reacted with heated nickel to produce Ni(CO)4, which is a gas and can therefore be separated from solid impurities:
Ni(s) + 4CO(g) ⇌ Ni(CO)4(g)
Given that the standard free energies of formation of CO(g) and Ni(CO)4(g) are −137.3 and −587.4 kJ/mol, respectively,
calculate the equilibrium constant of the reaction at 86.0°C.
Assume that ΔG o f is temperature-independent.

Respuesta :

Answer:

Explanation:

  • from ΔG = Summation of ΔGproducts - Summation of ΔGreactants
  • Given that the standard free energies of formation of CO(g) = −137.3
  • and Ni(CO)4(g)= −587.4 kJ/mol.
  • R = gas constant = 8.314
  • Temperature = 86.0°C +273 = 359k
  • ΔG reaction = −587.4 kJ/mol - (4 x −137.3kJ/mol) =  -38.2kJ/mol

  • From the vant hoff Isotherm equation ; ΔG = -RTlnk
  • lnk = -38.2kJ/mol / 359 x 8.314
  • lnk = -0.0127, k = 0.987

The equilibrium constant of the Mond process reaction Ni(s) + 4CO(g) ⇄ Ni(CO)₄(g) at 86 °C is 3.62x10⁵, given that the standard free energies of formation of CO(g) and Ni(CO)₄(g) are -137.3 and -587.4 kJ/mol, respectively.

The reaction of the Mond process is the following:

Ni(s) + 4CO(g) ⇄ Ni(CO)₄(g)   (1)

We can calculate the equilibrium constant of the above reaction with the equation:

[tex] \Delta G^{0} = -RTln(K) [/tex]   (2)

Where:

R: is the gas constant = 8.314 J/(K*mol)

T: is the temperature = 86.0 °C = 359 K

ΔG⁰: is the change in standard Gibbs free energy

K: is the equilibrium constant =?

The change in free energy is given by:  

[tex]\Delta G^{0} = \Sigma n_{p}\Delta G^{0}_{f}_{p} - \Sigma n_{r}\Delta G^{0}_{f}_{r}[/tex]

Where p is for products, r for reactants and n is the stoichiometric factors of the compounds

From reaction (1) we have that n for Ni(CO)₄ and CO is 1 and 4, respectively, so

[tex]\Delta G^{0} = \Delta G^{0}_{f}_{Ni(CO)_{4}} - 4\Delta G^{0}_{f}_{CO}[/tex]

The standard free energy of Ni is zero because it is in its standard state.

[tex] \Delta G^{0} = -587.4 kJ/mol - (-4*137.3 kJ/mol) = -38.2 kJ/mol [/tex]

By solving equation (2) for K and entering the values of the parameters, we have:

[tex] K = e^{-\frac{\Delta G^{0}}{RT}} = e^{-\frac{-38.2 \cdot 10^{3} J/mol}{8.314 J/(K*mol)*359 K}} = 3.62 \cdot 10^{5} [/tex]

Therefore, the equilibrium constant of the reaction is 3.62x10⁵.

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