The change of internal energy cU° in the combustion of C60 (s) is -25,968 kJ/mol

Question

The change of internal energy cU° in the combustion of C60 (s) is -25,968 kJ/mol @ 25°C. To do these problems each requires a balanced chemical equation. It is assumed that you can figure out the equation from the specific description of enthalpy.

a. What is the enthalpy of combustion, cH° of C60 (s)? ans. -25,968 kJ/mol See text section 3.3, p 78.

b. What is the enthalpy of formation, fH° of C60 (s)? ans. 2357 kJ/mol See text section 3.5, p 82.

c. What is the enthalpy of vaporization of C60 (s) to C (g) per mole of C (g)? ans. 677.4 kJ/mol See text section 3.1, p 70.

d. How does this compare with the enthalpy of vaporization of graphite and diamond to C (g)?

C(graphite) vaporization = 716.7 kJ/mol C(diamond) vaporization = 714. 8 kJ/mol.

For data to compare, look up fH° of carbon (diamond) and carbon (graphite) from the Table in the data section of our book.

Explanation / Answer

a. )

C60 + 60 O2 ------------------------> 60 CO2

cH° = H° products - H° reactants

          = -60 x -393.5 - 2357

         = - 23968 kJ/mol

b. )

cH° = -23968 kJ/mol

C60 (s) + 60 O2 (g ) ------------------------> 60 CO2   (g)

cH° = H°f (CO2) - { (H°f (O2) + H°f (C60 ) }

-23968 = -393.5 - {0 +H°f (C60 }

H°f (C60   = 2357 kJ/mol

c. What is the enthalpy of vaporization of C60 (s) to C (g) per mole of C (g)? ans. 677.4 kJ/mol

Hvap = S / T

note : you did not provide any table to calculate entropy . if this knows enthalpy of of vapourisation you can calculate

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