Question

Electromagnetic radiation of wavelength 242 nm is just sufficient to ionise the
sodium atom. Calculate the ionisation energy of sodium in kJ mol?
Answer in brief​

Answer 1

Answer:

Here,

wavelength ( λ ) = 242 nm = 2.42 × 10^-7 m

we know,

Energy ( E ) = hc/λ

here, h is Plank's constant

c is the speed of light

and λ is the wavelength of photons

so, E = 6.626 × 10^-34 Js × 3 × 10^8 m/s /2.42 × 10^-7 m

= 0.0821 × 10^-17 J / atom

0.0821 × 10^-17 J energy is sufficient for ionisation of one Na atom , so it is the ionisation energy of Na .

hence, I.E = 0.0821 × 10^-17 J/atom

= 0.0821 × 10^-17 × 6.022 × 10²² J/mol

= 4.945 × 10^5 J/mol

= 4.945 × 10² KJ/mol