Calculate the coulombic force of attraction between Ca2 + and O2 - in CaO, which

Question

Calculate the coulombic force of attraction between Ca2 + and O2 - in CaO, which has the NaCl-type structure?

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Explanation / Answer

We have to find the Coulombic force of attraction between Ca2 + and O2 - in CaO.

We know that, Coulomb's force of attraction is given by:

F = k q1 q2 / d2

charge on Ca2+ = 2 x 1.6 x 10-19 C = +3.2  x 10-19 C

charge on O2- = - 2 x 1.6 x 10-19 C = -3.2  x 10-19 C

Distance is very important to find the force of attraction, In this case the distance is inter-atomic seperation which can be determined as follows?:

d = R(Ca+) + R(O2-) [ where R is the ionic radius ]

R(Ca+) = 0.1 nm = 0.1 x 10-9 m

R(O2-) = 0.14 nm = 0.14 x 10-9 m

d =  0.1 x 10-9 m +  0.14 x 10-9 m = 0.24 x 10-9 m

Putting all the values in the expression of force we get,

F = - [9 x 109 x 3.2  x 10-19 x (- 3.2  x 10-19 ) / ( 0.24 x 10-9 )2] = 16 x 10-9 N

Hence, F = 16 x 10-9 N.

(PS: Multiple questions, answered the first one. Request you to put the other questions seperately... Thanks. Let me know if you have any query regarding the solution).

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