Question

Three gas phase systems are studied. The first consists of Ca²⁺ and S^2- at 300 nm; the second is two uranium nuclei separated by 154 pm and the third is a chloride ion and iodide ion positioned 45 Å apart. Answer the following questions without using a calculator.
Which of these systems will give a negative ΔE when separated to infinite distance? (Select all that apply.)

chloride and iodide

uranium nuclei

Ca²⁺ and S^2-

Which of these three systems has the largest magnitude electrostatic potential, E_el? (Select all that apply)
uranium nuclei

Ca²⁺ and S^2-

chloride and iodide

Answer 1

1 ) answer : Ca+2 and S-2

explanation :

CaS distance = 300 nm = 300 x 10^-9 m = 3 x 10^-7 m

Uranium nuclie distance = 154pm = 154 x 10^-12 = 1.54 x 10^-10 m

ClI distance= 45Ao = 45 x 10^-8 = 4.5 x 10^-7 m

so comparing these three uranium nuclie distance is smaller than the other. so we need to give more energy to seperate them . so for greater distance between Ca+2 and S-2 large . so little amount energy needed. so large delta E

2) largest magnitude of electrostatic potential for Ca+2 and S-2

explanation : because CaS is itself ionic compound. so there are electrostatic attractions works inbetween Ca+2 and S-2

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