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Distinguish between ionic bonding and polar covalent bonding - Leaving Cert Chemistry - Question (b) - 2011
Question (b)
Distinguish between ionic bonding and polar covalent bonding. Why do ionic substances conduct electricity when molten or dissolved in water but not in the solid sta... show full transcript
Worked Solution & Example Answer:Distinguish between ionic bonding and polar covalent bonding - Leaving Cert Chemistry - Question (b) - 2011
Step 1
Distinguish between ionic bonding and polar covalent bonding.
Answer
Ionic bonding refers to the bond formed from the electrostatic attraction between oppositely charged ions. This occurs due to the transfer (loss and gain) of electrons, resulting in the formation of positive and negative ions.
In contrast, polar covalent bonding involves the unequal sharing of bonding electrons between atoms. In polar covalent bonds, one atom has a slight positive charge (δ⁺), and the other has a slight negative charge (δ⁻), indicating that the electrons are not shared equally.
Step 2
Why do ionic substances conduct electricity when molten or dissolved in water but not in the solid state?
Answer
Ionic substances can conduct electricity when they are molten or dissolved in water because the ions are free to move. In a molten state or in solution, the ionic bonds are broken, allowing the ions to flow and carry electric charge.
Conversely, in a solid state, the ions are locked in a fixed position within a crystal lattice and cannot move, which prevents the conduction of electricity.
Step 3
Show that the ammonia molecule (NH₃) has polar covalent bonding.
Answer
The ammonia molecule has polar covalent bonding because there is an electronegativity difference between nitrogen (N) and hydrogen (H). Nitrogen has a greater electronegativity than hydrogen, leading to unequal sharing of the bonding electrons. The shared electrons are pulled closer to the nitrogen atom, resulting in a partial negative charge (δ⁻) on nitrogen and a partial positive charge (δ⁺) on the hydrogen atoms.
Step 4
Describe the processes involved when ammonia dissolves in water.
Answer
When ammonia dissolves in water, it forms hydrogen bonds with the water molecules. The ammonia molecule, which has a slightly negative region due to the nitrogen atom, interacts with the positively charged region of water (the hydrogen atoms). Similarly, the slightly positive hydrogen atoms of ammonia interact with the slightly negative oxygen atom of water. This interaction results in the formation of hydrogen bonds between water and ammonia, facilitating the solubility of ammonia in water.