Ionisation energy of lithium atom is 5.2 × 102 kJ mol -1. The wavelength of radiation sufficient to ionise sodium atom is

Question

Ionisation energy of lithium atom is 5.2 × 102 kJ mol -1. The wavelength of radiation sufficient to ionise sodium atom is (A) 0.0289 nm (B) 0.229 nm (C) 229 nm (D) 289 nm

Tardigrade Admin · Accepted Answer

I . E .=5.2 × 102 kJ mol -1=(5.2 × 105/6.023 × 1023) J atom -1 But E=(h c/λ) ∴ λ=(6.6 × 10-34 × 3 × 108 × 6.023 × 1023/5.2 × 105) =229 × 10-9 m =229 nm

Q. Ionisation energy of lithium atom is $5.2 \times 1 0^{2} k J m o l^{- 1}$ . The wavelength of radiation sufficient to ionise sodium atom is

$0.0289 nm$

$0.229 nm$

$229 nm$

$289 nm$

$I . E . = 5.2 \times 1 0^{2} k J m o l^{- 1} = \frac{5.2 \times 1 0 ^{5}}{6.023 \times 1 0 ^{23}} J a t o m^{- 1}$

But $E = \frac{h c}{λ}$

$∴ λ = \frac{6.6 \times 1 0 ^{- 34} \times 3 \times 1 0 ^{8} \times 6.023 \times 1 0 ^{23}}{5.2 \times 1 0 ^{5}}$

$= 229 \times 1 0^{- 9} m = 229 nm$

Q. Ionisation energy of lithium atom is 5.2×102kJmol−1. The wavelength of radiation sufficient to ionise sodium atom is

0.0289nm

0.229nm

229nm

289nm