Question

The energy required to break one mole of hydrogen-hydrogen bonds in $H_2$ is $436kJ$. What is the longest wavelength of light required to break a single hydrogen-hydrogen bond?

• A. $68.5nm$
• B. $137nm$
• C. $274nm$
• D. $548nm$

Answer 1

Answer: (C)

$274nm$

The energy required to break one mole of hydrogen-hydrogen bonds in $H_2$ is 436 kJ or 436,000 J.
The energy required to break a single hydrogen-hydrogen bond is $\frac{436,000}{6.023\times {10}^{23}}$ J.
$\lambda =\frac{hc}{E}=\frac{6.626\times {10}^{-34}\times 3\times {10}^8}{\frac{436,000}{6.023\times {10}^{23}}}=274\times {10}^{-9}m=274nm$
Hence, the longest wavelength of light required to break a single hydrogen-hydrogen bond is 274 nm.