PHYSICS · Multi-part · CBSE · Physics · Electrostatic Potential and Capacitance · Electrostatic Potential and Capacitance
Problem
Table 1 lists three isolated ion pairs. For each pair, the magnitude of the charge on each ion and the center–to–center separation distance are provided.
Table 1 — Ion-pair data
Ion Pair
Charge on Cation
Charge on Anion
Separation distance / pm
Pair X
+1
–1
240
Pair Y
+2
–1
240
Pair Z
+1
–1
120
Assume that only electrostatic attraction governs the interaction energy for these isolated ion pairs.
(a) Without performing a numerical calculation, rank the three ion pairs in order of increasing magnitude of attractive potential energy. Justify your ranking in terms of the variables that control electrostatic interaction strength.
(b) Describe qualitatively how the potential-energy versus separation-distance curve for Pair Y would differ from that of Pair X. Discuss both the position of the energy minimum and the depth of the well.
(c) Suppose the cation charge in Pair Z were doubled while the separation distance were simultaneously doubled. Explain whether the magnitude of the attractive potential energy would increase, decrease, or remain the same, and support your answer with proportional reasoning.