The maximum kinetic energy of the photoelectrons is found to be `6.63xx10^(-19)J`, when the metal is irradiated with a radiation of frequency `2xx10^(15)`Hz. The threshold frequency of the metal is about:

Answer

`199.51 kJ "mol"^(-1)`

Explanation

Energy of a photon (E)=hv
`h=6.626xx10^(-34) Js , v=5xx10^(14) Hz = 5xxx10^(14)s^(-1)`
`E=(6.626xx10^(-34)Js)xx(5xx10^(14)s^(-1))=3.313xx10^(-19)J`.
Energy of one mole photons
`=(3.313xx10^(-19)J)xx(6.022xx10^(23)"mol"^(-1))`
`=19.951xx10^(4) J "mol"^(-1)=199.51 kJ "mol"^(-1)=199.51 kJ "mol"^(-1)`