ThermochemistryHard

Question

Which of the following statement(s) is/are ture?

Options

A.ᐃE = 0 for combustion of C2H6(g) in a sealed rigid adiabatic container
B.fHo (S, monoclinic) ≠ 0
C.If dissociation energy of CH4 (g) is 1656 kJ/mol and C2H6(g) is 2812 kJ/mol, then value of C − C bond energy will be 328 kJ/mol
D.If ᐃHf(H2O,g) = - 242 kJ/mol; ᐃHvap (H2O, l) = 44 kJ/mol then ᐃfHo (OH- ,aq.) will be - 142 kJ/mol

Solution

(A) ᐃE will be - ve for combustion reactions
(B) ᐃHfo (S, rhombic) = 0
(C) CH4(g) → C(g) + 4H (g)     ᐃH = 1656 kJ/mole = 4 ∈C-H
      C2H6(g) → 2C(g)  + 6H (g)     ᐃH = 2812 kJ/mole = 6 ∈C-H + ∈C-C
      So  ∈C-C = (2812 - × 1656) kJ/mole  = 328 kJ/mole
(D) Can not be concluded from given data.

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