Physical Properties of Alkanes
1. Alkanes are almost non-polar molecules because:
a) They contain ionic bonds
b) The electronegativity difference between C and H is very small
c) They are soluble in water
d) They have high dipole moment
2. The intermolecular forces present in alkanes are:
a) Hydrogen bonding
b) Ionic forces
c) Weak van der Waals forces
d) Covalent bonding
3. The first four members of alkanes (C₁ to C₄) at 298 K are:
a) Liquids
b) Solids
c) Gases
d) Plasma
4. Alkanes from C₅ to C₁₇ at 298 K are:
a) Gases
b) Liquids
c) Solids
d) Crystalline
5. Alkanes containing 18 or more carbon atoms at 298 K are:
a) Gases
b) Liquids
c) Solids
d) Volatile
6. The colour of alkanes is:
a) Yellow
b) Green
c) Colourless
d) Blue
7. Alkanes are:
a) Odourless (except lower members)
b) Sweet smelling
c) Pungent smelling
d) Foul smelling
8. Which of the following best explains why alkanes are insoluble in water?
a) They are polar
b) They form hydrogen bonds with water
c) They are non-polar and hydrophobic
d) They are heavier than water
9. Petrol is used for dry cleaning of clothes to remove grease stains because:
a) Petrol is polar
b) Grease is polar
c) Like dissolves like – both are non-polar
d) Petrol reacts with grease
10. Which of the following statements is correct regarding solubility of alkanes?
a) Soluble in polar solvents
b) Soluble in non-polar solvents
c) Soluble in water
d) Soluble in acids
11. The boiling point of alkanes increases with increase in molecular mass because:
a) Hydrogen bonding increases
b) van der Waals forces increase
c) Ionic character increases
d) Covalent character decreases
12. Among pentane, 2-methylbutane, and 2,2-dimethylpropane, the highest boiling point is of:
a) Pentane
b) 2-Methylbutane
c) 2,2-Dimethylpropane
d) All have same boiling point
13. The boiling point of 2,2-dimethylpropane is lower than pentane because:
a) It has higher molecular mass
b) It has spherical shape → smaller surface area → weaker van der Waals forces
c) It is more polar
d) It forms hydrogen bonds
14. As branching in alkanes increases, the boiling point:
a) Increases
b) Decreases
c) Remains same
d) First increases then decreases
15. The melting point of alkanes generally:
a) Decreases with increase in molecular mass
b) Increases with increase in molecular mass
c) Shows irregular trend
d) Is constant
16. Which of the following alkanes is a gas at room temperature?
a) Pentane
b) Hexane
c) Butane
d) Octane
17. Which of the following alkanes is a solid at room temperature?
a) Methane
b) Ethane
c) Propane
d) Eicosane (C₂₀H₄₂)
18. The solubility of alkanes in water is:
a) High
b) Moderate
c) Very low or negligible
d) Complete
19. The density of alkanes is:
a) Greater than water
b) Less than water
c) Equal to water
d) Variable
20. Which of the following is responsible for the increase in boiling point from methane to decane?
a) Increase in hydrogen bonding
b) Increase in molecular size and surface area → stronger van der Waals forces
c) Increase in polarity
d) Increase in ionic character
Answer Key
| Q.No | Answer |
|——|——–|
| 1 | b |
| 2 | c |
| 3 | c |
| 4 | b |
| 5 | c |
| 6 | c |
| 7 | a |
| 8 | c |
| 9 | c |
| 10 | b |
| 11 | b |
| 12 | a |
| 13 | b |
| 14 | b |
| 15 | b |
| 16 | c |
| 17 | d |
| 18 | c |
| 19 | b |
| 20 | b |preapartion of alkanes Comparison of alkanes, alkenes, alkynes and arenes
