Question

A) Calculate the standard free-energy change at 25 ∘C for the following reaction:
Mg(s)+Fe2+(aq)→Mg2+(aq)+Fe(s)
Express your answer to three significant figures and include the appropriate units.
ΔG∘ =−3.71×105 J

B) Calculate the standard cell potential at 25 ∘C for the reaction
X(s)+2Y+(aq)→X2+(aq)+2Y(s)
where ΔH∘ = -629 kJ and ΔS∘ = -263 J/K .
Express your answer to three significant figures and include the appropriate units

Answer 1

Answer:

A) ΔG° = -3,80x10⁵ kJ

B) E° = 2,85V

Explanation:

A) It is possible to answer this problem using the standard ΔG's of formation. For the reaction:

Mg(s) + Fe²⁺(aq) → Mg²⁺(aq) + Fe(s)

The ΔG° of reaction is:

ΔG° = ΔGFe(s) + ΔGMg²⁺(aq) - (ΔGFe²⁺(aq) + ΔGMg(s) (1)

Where:

ΔGFe(s): 0kJ

ΔGMg²⁺(aq): -458,8 kJ

ΔGFe²⁺(aq): -78,9 kJ

ΔGMg(s): 0kJ

Replacing in (1):

ΔG° = 0kJ -458,8kJ - (-78,9kJ + okJ)

ΔG° = -3,80x10² kJ ≡ -3,80x10⁵ kJ

B) For the reaction:

X(s) + 2Y⁺(aq) → X²⁺(aq) + 2Y(s)

ΔG° = ΔH° - (T×ΔS°)

ΔG° = -629000J  - (298,15K×-263J/K)

ΔG° = -550587J

As ΔG° = - n×F×E⁰

Where n are electrons involved in the reaction (2mol), F is faraday constant (96485 J/Vmol) And E° is the standard cell potential

Replacing:

-550587J = - 2mol×96485J/Vmol×E⁰

E° = 2,85V

I hope it helps!

Answer 2

The free energy is related to the standard cell potential.

We know that the standard free energy is obtained from;

• ΔG = -nFEcell
• ΔG = change in free energy
• F = Faraday constant
• n = number of electrons transferred
• Ecell = standard cell potential

In question A;

Ecell = (-0.44 V) - (-2.37 V)

Ecell = 1.93 V

ΔG∘ = -(2 × 96500 ×  1.93)

ΔG∘ = −3.71×105 J

In question B

We have to first obtain ΔG∘  as follows;

ΔG∘ = ΔH∘ - T ΔS∘

ΔG∘ = -629 ×10^3 J - [298 K × (-263 J/K)]

ΔG∘ = -550626 J

But;

ΔG∘ = -nFEcell

Ecell = ΔG∘/-nF

Ecell = -550626 J/-(2 × 96500)

Ecell = 2.85 V

Learn more about free energy: https://brainly.com/question/1217654