Notifications
Clear all
0
25/09/2021 3:34 pm
Topic starter
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 (Avogadro number = 6.02 × 1023 mol-1, h = 6.62 × 10-34 J s):
(a) 2.48 × 104 nm
(b) 1.49 × 103 nm
(c) 2.48 × 103 nm
(d) 1.49 × 104 nm
1 Answer
0
25/09/2021 3:46 pm
Correct answer: (b) 1.49 × 103 nm
Explanation:
In CH4, 4 × BE(C – H) = 360 kJ/mol
∴ BE(C – H) = 90 kJ/mol
In C2H6, BE(C – C) + 6 × BE(C – H) = 620 kJ/mol
∴ BE(C – C) = 80 kJ/mol
∴ BE(C – C) = \(\frac{80 \times 10^3}{6.023 \times 10^23}\) J/molecule
Now, E = \(\frac{hc}{\lambda}\)
∴ λ = \(\frac{6.626 \times 10^{34} \times 3 \times 10^8 \times 6.023 \times 10^{23}}{80 \times 10^3}\)
∴ λ = 1.49 x 103 nm