Question

Which of the below property is shown by all ionic compound?
• High volatility
• Very poor electrical conductivity below the melting point
• Low boiling point
• High solubility in water

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

Remember:
• Solid ionic compounds do not conduct electricity because ions are fixed.
• Molten or aqueous ionic compounds conduct electricity because ions become free to move.
• Ionic compounds usually have high melting and boiling points due to strong electrostatic forces.

Answer 1

The Correct Option is B

Concept: Ionic compounds are formed due to the electrostatic force of attraction between positively charged ions (cations) and negatively charged ions (anions). These forces are extremely strong and hold the ions rigidly in a crystal lattice structure. Some important physical properties of ionic compounds are:
• They usually have high melting and boiling points.
• In solid state, ions are fixed in position and cannot move freely.
• Since ions cannot move in solid state, ionic compounds do not conduct electricity in solid form.
• When melted or dissolved in water, ions become free to move and hence conduct electricity.
• Many ionic compounds are soluble in water due to the polar nature of water molecules. Thus, electrical conductivity depends upon the mobility of ions.

Step 1: Analyzing Option (1): High volatility. Volatility refers to the tendency of a substance to vaporize easily. Ionic compounds contain very strong electrostatic forces between oppositely charged ions. A large amount of energy is required to separate these ions. Therefore, ionic compounds generally do not vaporize easily and hence are not highly volatile. So, Option (1) is incorrect.

Step 2: Analyzing Option (2): Very poor electrical conductivity below the melting point. Below the melting point, ionic compounds exist in solid crystalline form. In this state:
• The ions are tightly packed.
• The ions are fixed at their lattice positions.
• There are no free ions available for movement. Electric current in ionic compounds is carried by the movement of ions. Since ions cannot move in solid state, ionic compounds show extremely poor electrical conductivity below their melting point. This property is shown by all ionic compounds. Hence, Option (2) is correct.

Step 3: Analyzing Option (3): Low boiling point. Ionic compounds possess strong interionic attractive forces. A very high amount of heat energy is required to overcome these forces and convert the liquid into vapor. Therefore, ionic compounds generally have high boiling points, not low boiling points. Thus, Option (3) is incorrect.

Step 4: Analyzing Option (4): High solubility in water. Many ionic compounds dissolve in water because water is a polar solvent. However, not all ionic compounds are highly soluble in water. Some ionic compounds are only slightly soluble or even insoluble. For example:
• Silver chloride (\(\mathrm{AgCl}\)) is insoluble in water.
• Barium sulfate (\(\mathrm{BaSO_4}\)) is also insoluble. Hence, this property is not true for all ionic compounds. Therefore, Option (4) is incorrect. Final Conclusion: The property shown by all ionic compounds is: \[ \boxed{\text{Very poor electrical conductivity below the melting point}} \] Hence, the correct answer is: \[ \boxed{(2)} \]