Chemical BondingHard
Question
The heat of atomization of methane and ethane are 360 kJ/mol and 620 kJ/mol, respectively. The longest wavelength of light capable of breaking the C-C bond is (A vogadro number = 6.02 × 1023, h = 6.62 × 10-34 J s):
Options
A.2.48 × 103 nm
B.1.49 × 103 nm
C.2.49 × 104 nm
D.2.48 × 104 nm
Solution
CH4(g) → C(g) + 4H(g)
⇒ 4 × EC - H = 360 KJ/Mol. ⇒ EC - H = 90 KJ/Mol.
and C2H6(g) → 2C(g) + 6H(g)
⇒ EC - C + 6 × 90 = 620 ⇒ EC - C = 80 kJ/mol
⇒ NA ×
= 80 × 1000 J
= 14.9 × 10-7 m = 1.49 × 10-6 m
= 1.49 × 103 nm.
⇒ 4 × EC - H = 360 KJ/Mol. ⇒ EC - H = 90 KJ/Mol.
and C2H6(g) → 2C(g) + 6H(g)
⇒ EC - C + 6 × 90 = 620 ⇒ EC - C = 80 kJ/mol
⇒ NA ×
= 80 × 1000 J= 14.9 × 10-7 m = 1.49 × 10-6 m
= 1.49 × 103 nm.
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