The coulombic force between two ions is reduced to of its original strength when the distance between them is quadrupled.

Explanation:

According to the coulombs law, the force existing vetween the ions is expressed as;

F = kQq/r² 1

Q and q are the ions

r is the distance between the ions

If the distance between the ion is quadrupled, then;

F2 =  kQq/(4r)²

F2 =  kQq/16r² ... 2

Divide equation 2 by 1;

F2/F = kQq/16r² ÷ kQq/r²

F2/F = kQq/16r² × r²/kQq

F2/F = 1/16

F2 = 1/16 F

Therefore the coulombic force between two ions is reduced to 1/16 of its original strength when the distance between them is quadrupled.

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