The molar enthalpy of fusion of solid silicon is 46.4 kJ mol -1 , and the molar

Question

The molar enthalpy of fusion of solid silicon is 46.4 kJ mol-1, and the molar entropy of fusion is 27.6 J K-1 mol-1.

(a) Calculate the Gibbs free energy change for the melting of 1.00 mol of silicon at 1.71×103 K.

_______ kJ

(b) Calculate the Gibbs free energy change for the conversion of 5.59 mol of solid silicon to liquid silicon at 1.71×103 K.

________ kJ

(c) Will silicon melt spontaneously at 1.71×103 K? _____ (Yes/No)


(d) At what temperature are solid and liquid silicon in equilibrium at a pressure of 1 atm?

_______ K

Explanation / Answer

(a)

Gibbs free energy change = delta H - T (deltaS)

= 46.4 - 1.71 * 103 (0.0276)

= - 0.796 kJ/mol

(b) Gibbs free energy change of 5.59 mol = - 5.59 * 0.796 = - 4.45 kJ

(c) Yes. Because gibbs free energy change has negative sign indicating spontaneous reaction.

(d)

Solid and liquid Silicon are in equilibrium, if delta G = 0

(OR) delta H - T delta S = 0

delta H = T delta S

T = delta H / Delta S

T = 46.4 / 0.0276

at T = 1.68 * 103 K the system is at equilibrium

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.