Question

Electromagnetic radiation of wavelength 242 nm is just sufficient to ionise the sodium atom. Calculate the ionisation of sodium in kJ mol${}^{-1}$.

• A. $2.8\times {10}^{-19}kJ/mole$
• B. $229kJ/mole$
• C. $495kJ/mole$
• D. $8.2\times {10}^{-19}kJ/mole$

Answer 1

The correct option is C $495kJ/mole$

$\Phi =\frac{hc}{\lambda }=\frac{hc}{242\times {10}^{-9}}$

$=8.2\times {10}^{-19}J/atom$

$=8.2\times {10}^{-19}\times NaJ/atom$

$=494.666\times {10}^{3}J/mole$

$=495kJ/mole$