Question

It takes 281.7 kJ of energy to remove 1 mole of electrons from the atoms on the surface of lithium metal. If lithium metal is irradiated with 261-nm light, what is the maximum kinetic energy the released electrons can have

Answer 1

The maximum kinetic energy of electron is = 2.93 ×
`10^(-19)` Joule

Step-by-step explanation:

We know that total energy

`E = (hc)/(\lambda)` ------------ (1)

Here h = plank's constant = 6.62 ×
`10^(-34)` J s

c = speed of light = 3 ×
`10^(8)`
`(m)/(s)`

`\lambda` = 261 nm = 261 ×
`10^(-9)` m

Put all these values in equation (1) we get

E = 7.6 ×
`10^(-19)` J

We know that

Total energy = Energy to remove an electron + K.E of electron

Energy to remove an electron =
`(281.7 (1000))/((6.023)10^(23) )`

Energy to remove an electron = 4.67 ×
`10^(-19)` J

K.E of electron = Total energy - Energy to remove an electron

K.E of electron = 7.6 ×
`10^(-19)` - 4.67 ×
`10^(-19)`

K.E of electron = 2.93 ×
`10^(-19)` Joule

Therefore the maximum kinetic energy of electron is = 2.93 ×
`10^(-19)` Joule