When we dissolve NaCl in H2O, does there exist any reaction??? I mean, does the Na take the place of H2 and becomes NaO??? Or something else??? Otherwise, how does water takes apart the ions that consist NaCl???
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Dissolution is not a chemical change, understand that even after dissolving NaCl into water it still remains an aqueous solution of NaCl. Actually when a salt is added to water then permanent dipoles of water pull the Na+ and Cl- ions apart from the crystal lattice. Now the forces holding these ions in the lattice are the lattice forces (ionic) and the forces exerted by water molecules are the dipole forces. If Ion - Dipole forces are more than the lattice forces then the ions dismantle from the lattice and get hydrated ie they dissolve. Many salts dont dissolve in water and form precipitates. Normally their lattice energies are higher than their hydration energies so their ions remain intact within the lattice and do not disperse.