Question

Which is an example of dissociation?
C + O2 mc003-1.jpg CO2
NH3 + H2O mc003-2.jpg NH4+ + OH–
SO2 + H2O mc003-3.jpg HSO3– + H+
Ca3(PO4)2 mc003-4.jpg 3Ca2+ + 2PO43–

Answer 1

Ca3(PO4)2 → 3Ca2+ + 2PO4^3–

This is dissociation: an ionic solid separating into its constituent ions in solution. The others are formation/combustion (C + O2 → CO2) or acid/base proton transfer reactions rather than simple ionic dissociation.