Be sure to answer all parts. Write equations for the oxidation of Fe and of Al. Use ΔG o f to determine whether either process is spontaneous at 25°C. (a) Equation for oxidation of iron: ΔG o rxn : kJ Is the oxidation of iron spontaneous at 25°C? yes no (b) Equation for the oxidation of aluminum: ΔG o rxn : kJ Is the oxidation of aluminum spontaneous at 25°C? yes no

(a) Fe (s) ⇒ Fe²⁺ (aq) + 2 e⁻

ΔG° = - 85 kJ

Spontaneous

(b) Al (s) ⇒ Al³⁺ (aq) + 3 e⁻

ΔG° = - 480 kJ

Spontaneous

Explanation:

(a) The equation for the oxidation of iron is:

Fe (s) ⇒ Fe²⁺ (aq) + 2 e⁻ E° = 0.44 V

We can calculate the standard Gibbs free energy (ΔG°) using the following expression.

ΔG° = - n. F. E°

where,

n are the moles of electrons transferred

F is the Faraday's constant

ΔG° = - 2 mol * (96,468 * 10⁻³ kJ/V. mol) * 0.44 V = - 85 kJ

ΔG° < 0, which means that the reaction is spontaneous.

(b) The equation for the oxidation of aluminum is:

Al (s) ⇒ Al³⁺ (aq) + 3 e⁻ E° = 1.66 V

ΔG° = - 3 mol * (96,468 * 10⁻³ kJ/V. mol) * 1.66 V = - 480 kJ

ΔG° < 0, which means that the reaction is spontaneous.