Question

100.The energy required to break one mole of Cl - Cl bonds Cl2 is 242 Kj /mol . the longest wavelength of light capable of breaking a single Cl – Cl bond is
(c = 3 x 10^8 m/s and N to the base A = 6.02 x 10^23 /mol)
1.494 nm
2.594 nm
3.640 nm
4.700 nm

Correct ans is 1. I want the explanation.

Answer 1

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Answer 2

Answer: The longest wavelength of light capable of breaking a single Cl-Cl bond is 494 nm.

Explanation;

$c=3\times 10^8 m/s$

$N_ A=6.02\times 10^23 mol^{-1}$

Energy required to break one mole of Cl-Cl bonds = 242 kJ /mol

Energy required to break one molecule of Cl-Cl bond:$E'$

$E'=\frac{242 kJ/mol}{6.02\times 10^{23} mol^{-1}}=4.0199\times 10^{-22} kJ=4.0199\times 10^{-19} J$

$\lambda =\frac{hc}{E'}=\frac{6.626\times 10^{-34} Js\times 3\times 10^8 m/s}{4.0199\times 10^{-19} J}=4.94\times 10^{-7}=494 nm ,(1 nm=10^{-9}m)$

The longest wavelength of light capable of breaking a single Cl – Cl bond is 494 nm.