An aqueous solution is prepared by dissolving calcium nitrate, Ca(NO₃)₂(s), in water. After complete dissociation, the mixture contains Ca²⁺ cations and polyatomic NO₃⁻ anions dispersed among many water molecules.
(a) Compare the relative strengths of the ion–dipole interactions between a single water molecule and (i) Ca²⁺ versus (ii) NO₃⁻. In your explanation, consider both charge magnitude and average ion–water distance.
(b) Experimental evidence suggests that six water molecules occupy the first solvation shell around Ca²⁺. Describe how these six water molecules should be oriented, referencing the parts of the water molecule nearest the ion.
(c) The nitrate ion is planar and bears its negative charge primarily on the three oxygen atoms. Describe how water molecules in the first solvation shell will orient themselves around a single NO₃⁻, and explain why this orientation differs from that around Ca²⁺.
(d) Predict qualitatively how increasing the concentration of Ca(NO₃)₂ would affect the average geometric "perfection" (orientation fidelity) of water molecules in the first solvation shells of both Ca²⁺ and NO₃⁻. Justify your prediction.