Question

When two identical ions are separated by a distance of 4.2×10−10 , the electrostatic force each exerts on the other is 5.2×10−9 ?

Answer 1

F = kq2 / r2 
q = ne 
 F = k(ne)2 / r2 
 n = âš(r2F / ke2) = (r/e) âš(F/k) 
 k = 9 x 109 Nm2/C2 
 e = 1.6 x 10-19 C 
 n = [(4.2 x 10-10) / (1.6 x 10-19)] âš[(5.2 x 10-9) / (9 x 109)] ≅ 1.995 ≅ 2