Question

(a) Give reason for the following :
(i) Ionic compounds have high melting and boiling points.
(ii) Ionic compound are soluble in water.
(iii) Ionic compounds conduct elecincity in molten state.
(b) Show the formation of MgO by transfer of electrons.


CBSE Class X Science LA (5 Marks)

Answer 1

(a) (i) Ionic compounds have high melting and boiling points. It is because of strong force of attraction between oppositely charged ions, therefore high energy is required to break the metallic bonds between ions.

(ii)  Ionic compounds are soluble in water because they form ions in aqueous solutions.

(iii) tonic compounds conduct electricity in molten state and in aqueous solution because ions carry current. The movement of ions takes place towards oppositely charged electrode in electric field.

(b) Formation of MgO:
For this, open the attachment.

Answer 2

A higher melting/boiling point than what? Ionic compounds are NON-MOLECULAR species, and each ion in the lattice is electrostatically attracted to every other counter-ion in the lattice by Coulomb’s law. Of course, each such ion is electrostatically repelled by every other ion of the same charge in the lattice, but if you sum up the attractive and repulsive interactions, and this may be certainly performed quantitatively, a NET ATTRACTIVE FORCE results, and this adds to the lattice energy of the salt…

As a non-molecular species, we would expect high melting, and boiling points…and certainly this expectation is realize..