The required to separate the ion pair = ##4.297xx10^(-19)”J”## I have assumed a copper(II) ion and

The required to separate the ion pair = ##4.297xx10^(-19)”J”##
I have assumed a copper(II) ion and an electrostatic model.

For 2 charges ##q_1## and ##q_2## separated by a distance ##r## the force of attraction is given by :
##F=(1)/(4piepsilon_0).(q_1q_2)/(r^2)##
The constant ##(1)/(4piepsilon_0)## can be written as ##k## and has the value ##9xx10^(9)”m/F”##
The done in separating the 2 charges from ##r## to infinity is given by:
##W=-k.(q_1q_2)/(r) ” “color(red)((1))##
I will assume a wholly electrostatic model where we have discrete ions in contact.
The ionic radii are:
##r^+=87″pm”## for ##Cu^(2+)##
##r^(-)=126″pm”## for ##O^(2-)##
This means the total distance between the centre of the 2 ions is:
##126+87=213″pm”=r##
The electronic charge = ##-1.602xx10^(-19)”C”##
So the charge on the ##Cu^(2+)## ion =
##+2(1.602xx10^(-19))=+3.204xx10^(-19)”C”##
The charge on the ##O^(2-)## must therefore be:
##-3.204xx10^(-19)”C”##
Putting these values into ##color(red)((1))rArr##
##W=-(9xx10^(9)xx(3.204xx10^(-19))xx(-3.204xx10^(-19)))/(215xx10^(-12))color(white)(x)J##
##W=4.297xx10^(-19)”J”##