Questions about Straight-Chain Alkanes (Organic Chemistry)
20 multiple-choice questions about Straight-Chain Alkanes in Organic Chemistry, each with five alternatives (A–E). The answers with extended explanations are included at the end.
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Straight-Chain Alkanes — Multiple Choice Questions
1. What is the general formula for straight-chain alkanes?
A) CnH2n
B) CnH2n+2
C) CnHn
D) CnH2n−2
E) CnH2nO2
2. What type of bonds do alkanes contain?
A) Only double bonds
B) Only triple bonds
C) Ionic bonds
D) Only single covalent bonds
E) Metallic bonds
3. What is the IUPAC name for C₂H₆?
A) Methane
B) Ethane
C) Ethene
D) Ethyne
E) Propane
4. What is the IUPAC name for the straight-chain alkane with 3 carbon atoms?
A) Methane
B) Butane
C) Pentane
D) Propane
E) Hexane
5. Which of the following straight-chain alkanes has 5 carbon atoms?
A) Butane
B) Propane
C) Pentane
D) Hexane
E) Ethane
6. Which of the following is NOT a straight-chain alkane?
A) Methane
B) Ethane
C) Propane
D) Cyclohexane
E) Butane
7. What is the main characteristic of straight-chain alkanes?
A) They contain aromatic rings
B) They contain branched structures
C) All carbon atoms are connected in a continuous chain
D) They are unsaturated
E) They have at least one double bond
8. What is the name of the straight-chain alkane with 10 carbon atoms?
A) Octane
B) Decane
C) Nonane
D) Dodecane
E) Heptane
9. What state of matter are the first four straight-chain alkanes at room temperature?
A) Solids
B) Liquids
C) Gases
D) Plasmas
E) Colloids
10. What happens to the boiling point of straight-chain alkanes as the number of carbon atoms increases?
A) It decreases
B) It remains constant
C) It increases
D) It fluctuates randomly
E) It becomes zero
11. Which straight-chain alkane has the chemical formula C₆H₁₄?
A) Hexane
B) Pentane
C) Butane
D) Heptane
E) Octane
12. What kind of reaction do alkanes commonly undergo with halogens?
A) Addition
B) Substitution
C) Elimination
D) Polymerization
E) Hydrolysis
13. Which of the following alkanes has the highest boiling point?
A) Methane
B) Ethane
C) Butane
D) Octane
E) Propane
14. What is the name of the alkane with the molecular formula C₄H₁₀?
A) Methane
B) Butane
C) Propane
D) Pentane
E) Hexane
15. What is the first member of the straight-chain alkane series?
A) Ethane
B) Propane
C) Methane
D) Butane
E) Pentane
16. Straight-chain alkanes are also known as:
A) Cycloalkanes
B) Aromatic hydrocarbons
C) Paraffins
D) Olefins
E) Alkynes
17. What is the total number of hydrogen atoms in butane (C₄H₁₀)?
A) 4
B) 6
C) 8
D) 10
E) 12
18. The combustion of a straight-chain alkane in excess oxygen produces:
A) CO and H₂O
B) CO₂ and H₂O
C) CH₄ and H₂
D) C and CO
E) CO₂ and O₂
19. Which straight-chain alkane is a major component of natural gas?
A) Butane
B) Ethane
C) Methane
D) Hexane
E) Octane
20. What type of isomerism is NOT shown by straight-chain alkanes?
A) Structural isomerism
B) Chain isomerism
C) Position isomerism
D) Geometrical isomerism
E) Constitutional isomerism
✅ Answer Key with Extended Explanations
1. B – The general formula for alkanes is CnH2n+2, where n is the number of carbon atoms.
2. D – Alkanes are saturated hydrocarbons and contain only single covalent bonds.
3. B – C₂H₆ is called ethane, a two-carbon alkane.
4. D – Propane has 3 carbon atoms in a straight chain: CH₃–CH₂–CH₃.
5. C – Pentane contains 5 carbon atoms and is an alkane.
6. D – Cyclohexane is a cyclic alkane, not a straight-chain.
7. C – In straight-chain alkanes, carbon atoms are connected in an unbranched linear chain.
8. B – Decane has 10 carbon atoms and follows the alkane naming pattern.
9. C – Methane, ethane, propane, and butane are gases at room temperature.
10. C – Boiling point increases with longer carbon chains due to stronger van der Waals forces.
11. A – C₆H₁₄ is hexane, a straight-chain alkane with six carbon atoms.
12. B – Alkanes react with halogens via substitution reactions (e.g., methane with chlorine).
13. D – Octane has the longest chain among the options, giving it the highest boiling point.
14. B – Butane has 4 carbon atoms and 10 hydrogen atoms: C₄H₁₀.
15. C – Methane (CH₄) is the simplest alkane and the first in the homologous series.
16. C – Straight-chain alkanes are also called paraffins, particularly in industry.
17. D – Butane contains 10 hydrogen atoms: C₄H₁₀.
18. B – Complete combustion of alkanes in oxygen yields CO₂ and H₂O.
19. C – Methane (CH₄) is the main component of natural gas.
20. D – Geometrical (cis-trans) isomerism does not occur in alkanes since they lack double bonds.
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