Common salt or sodium chloride (NaCI) is an ionic compound, in which Na* ion and CI" ions are held together by electrostatic forces. Charges on Na and Cl ions are

determined to be+0.5.e and –0.5.e, respectively, (where e is the charge of an electron) while the distance between Na and Cl ions in a NaCl face-centred cubic crystal is 280 picometers. (a) (9 MARKS) Calculate the Coulomb force between the sodium and chloride ions by assuming the following dielectric constants (D) for three different media. i. D= 1 for air ii.D = 25 for 100% pure drinking alcohol (ethanol) iii.D = 80 for pure water