Anand Classes provides comprehensive notes on the Properties of Covalent Compounds for Class 11 Chemistry. Covalent compounds show characteristic features like low melting and boiling points, poor electrical conductivity, solubility in non-polar solvents, and molecular nature due to shared electron pairs. These notes include detailed explanations, solved questions, MCQs, and Q&A sets for CBSE, JEE, and NEET exam preparation. Click the print button to download study material and notes.
General Properties of Covalent Compounds
Covalent compounds show characteristic physical and chemical properties because their atoms are held together by shared electron pairs rather than by electrostatic forces. The main properties are discuss in next sections
1. State of Existence
- Covalent compounds exist as molecules, not as ions.
- Weak intermolecular forces (van der Waals forces) hold these molecules together.
- As a result, most covalent compounds exist as liquids or gases at room temperature.
- A few exceptions exist in the solid state, such as urea and sugar.
2. Low Melting and Boiling Points
- Due to weak intermolecular forces, covalent compounds have low melting and boiling points.
- Only a small amount of energy is required to overcome these weak forces.
- Example: Ice (solid H₂O) melts at 273 K, while sodium chloride (ionic) melts at 1074 K.
3. Solubility
- Covalent compounds are generally insoluble in water and other polar solvents.
- They are soluble in non-polar solvents such as:
- Benzene (C6H6)
- Carbon tetrachloride (CCl4)
- Ether
This follows the principle “like dissolves like”.
4. Non-Conductors
- Covalent compounds do not produce ions in solution.
- Therefore, they are poor conductors of electricity in both fused (molten) and aqueous states.
5. Molecular Reactions
- Reactions between covalent compounds occur molecule to molecule.
- These reactions involve:
- Breaking of covalent bonds in reactants.
- Formation of new covalent bonds in products.
- Since breaking covalent bonds requires energy, such reactions are generally slow.
6. Directional Character of Bond
- A covalent bond is formed by localized electron sharing between two nuclei.
- This bond is directional in nature, meaning atoms bond at specific angles to achieve maximum overlap of orbitals.
- This explains the definite shapes of molecules like:
- H2O (bent shape, bond angle ≈ $104.5^\circ$)
- CH4 (tetrahedral, bond angle ≈ $109.5^\circ$)
FAQs on General Properties of Covalent Compounds
Q1. Why do most covalent compounds exist as gases or liquids at room temperature?
Because they are made of neutral molecules held together by weak intermolecular forces (van der Waals or dipole–dipole), which require little energy to separate.
Q2. Why do covalent compounds have low melting and boiling points?
Breaking a covalent solid involves overcoming weak molecule–molecule attractions, not strong ionic forces.
Q3. Are covalent compounds soluble in water?
Generally no, because water is polar and cannot effectively interact with neutral covalent molecules.
However, covalent compounds may dissolve in non-polar solvents like benzene or CCl4.
Q4. Why are covalent compounds poor conductors of electricity?
They lack free ions or electrons in solution or molten form.
Q5. What gives covalent bonds their directional nature?
Covalent bonds are formed by localized overlap of atomic orbitals, so the atoms bond in specific spatial orientations, leading to definite molecular shapes.
MCQs on General Properties of Covalent Compounds
1. Covalent compounds generally have:
(a) High melting points
(b) Low melting points
(c) Good electrical conductivity
(d) High solubility in water
Answer: (b) Low melting points
2. The solubility of covalent compounds is best explained by:
(a) Lattice energy
(b) Dielectric constant
(c) Like dissolves like principle
(d) Ionization potential
Answer: (c) Like dissolves like principle
3. Which of the following is a solid covalent compound at room temperature?
(a) CH4
(b) HCl
(c) Urea
(d) CO2
Answer: (c) Urea
Assertion–Reason Questions on General Properties of Covalent Compounds
Assertion (A): Covalent compounds are poor conductors of electricity.
Reason (R): They do not form ions in the molten or aqueous state.
- (a) Both A and R are true, and R is the correct explanation of A.
- (b) Both A and R are true, but R is not the correct explanation of A.
- (c) A is true, R is false.
- (d) A is false, R is true.
Answer: (a)
Assertion (A): Covalent bonds are directional in nature.
Reason (R): Covalent bonds arise from the sharing of electron pairs between two atoms, leading to localized electron density.
- (a) Both A and R are true, and R is the correct explanation of A.
- (b) Both A and R are true, but R is not the correct explanation of A.
- (c) A is true, R is false.
- (d) A is false, R is true.
Answer: (a)
Case Study on General Properties of Covalent Compounds
Read the following passage and answer the questions:
Carbon tetrachloride (CCl4) is a covalent compound that exists as a colorless liquid at room temperature. It is insoluble in water but readily dissolves in benzene. When dissolved in benzene, it does not conduct electricity.
Questions:
- Why does CCl4 dissolve in benzene but not in water?
- Why is CCl4 a poor conductor of electricity?
- Predict the physical state of CCl4 at room temperature and justify.
Answers:
- Because both CCl4 and benzene are non-polar (like dissolves like).
- CCl4 is molecular and produces no free ions.
- It exists as a liquid due to weak intermolecular forces between molecules.
Key Takeaway
Covalent compounds differ from ionic compounds by their molecular nature, low melting/boiling points, solubility in non-polar solvents, and directional bonding, all of which arise from the sharing of electrons rather than the transfer of electrons.