Calculate the standard free-energy change for the reaction at 25 ∘ C. 25 ∘C. Refer to the list of standard reduction potentials. 2 Au 3 + (aq) + 3 Ni (s) − ⇀ ↽ − 2 Au (s) + 3 Ni 2 + (aq) 2Au3+(aq)+3Ni(s)↽−−⇀2Au(s)+3Ni2+(aq) Δ G ∘ = ΔG∘=

Respuesta :

Answer: The [tex]\Delta G^o[/tex] for the given reaction is [tex]-1.02\times 10^6J[/tex]

Explanation:

For the given chemical reaction:

[tex]2Au^{3+}(aq.)+3Ni(s)\rightarrow 3Ni^{2+}(aq.)+2Au(s)[/tex]

Here, gold is getting reduced because it is gaining electrons and nickel is getting oxidized because it is loosing electrons.

Oxidation half reaction:  [tex]Ni(s)\rightarrow Ni^{2+}(aq.)+2e^-[/tex]   ( × 3)

Reduction half reaction:  [tex]Au^{3+}(aq.)+3e^-\rightarrow Au(s)[/tex]   ( × 2)

We know that:

[tex]E^o_{(Au^{3+}/Au)}=1.50V\\E^o_{(Ni^{2+}/Ni)}=-0.23V[/tex]

Substance getting oxidized always act as anode and the one getting reduced always act as cathode.

To calculate the [tex]E^o_{cell}[/tex] of the reaction, we use the equation:

[tex]E^o_{cell}=E^o_{cathode}-E^o_{anode}[/tex]

[tex]E^o_{cell}=1.50-(-0.23)=1.73V[/tex]

Relationship between standard Gibbs free energy and standard electrode potential follows:

[tex]\Delta G^o=-nFE^o_{cell}[/tex]

where,

n = number of electrons transferred = 6

F = Faraday's constant = 96500 C

[tex]E^o_{cell}[/tex] = standard cell potential = 1.73 V

Putting values in above equation, we get:

[tex]\Delta G^o=-6\times 96500\times 1.73=-1001670J=-1.02\times 10^6J[/tex]

Hence, the [tex]\Delta G^o[/tex] for the given reaction is [tex]-1.02\times 10^6J[/tex]

The standard free energy is - 1002 kJ.

Recall the formula;

ΔG∘ = -nFE∘cell

  • ΔG∘ = change in free energy
  • n = number of moles of electrons transferred
  • F = Faraday constant
  • E∘cell = standard cell potential

E∘cell = 1.50 V - (-0.23 V) = 1.73 V

Applying the formula above;

ΔG∘= -(6 × 96500 ×  1.73 V)

ΔG∘= - 1002 kJ

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