Monday 21 February 2022

Class 11 - Chemistry - Alkanes - Questions and Answers #hydrocarbons #alkanes #organicchemistry #class11chemistry #eduvictors

Class 11 - Chemistry - Alkanes - Questions and Answers

Class 11 - Chemistry - Alkanes - Questions and Answers #hydrocarbons #alkanes #organicchemistry #class11chemistry #eduvictors

Chapter: Hydrocarbons

Very Short Answer Based Questions (VSQA)

Q1: What are hydrocarbons?

Answer: Hydrocarbons are the compounds of carbon and hydrogen are obtained from coal and petroleum.

Q2: What are alkanes?

Answer: Alkanes are saturated open-chain hydrocarbons containing C—C single bonds.

Q3: How C-C atoms are joined in alkanes? What are the lengths of C-C and C-H bonds?

Answer:  In alkanes, C-atoms are tetrahedrally joined together in which C—C and C—H bond lengths are 154 pm and 112 pm respectively.

Q4: What type of hybridisation is found in C-atoms of alkanes?

Answer: All the C-atoms in alkanes are sp³ -hybridised.

Q5: Draw the structure of a methane molecule?


Class 11 - Chemistry - Alkanes - Questions and Answers #hydrocarbons #alkanes #organicchemistry #class11chemistry #eduvictors

Q6: What is the generic formula for alkanes?

Answer: CₙH₂ₙ₊₂

Q7: List the names of the first ten alkane members


No. of C-atoms Formula (I) Formula (II) Name
1 CH₄ CH₄ Methane
2 C₂H₆ CH₃CH₃ Ethane
3 C₃H₈ CH₃CH₂CH₃ Propane
4 C₄H₁₀ CH₃(CH₂)₂CH₃ Butane
5 C₅H₁₂ CH₃(CH₂)₃CH₃ Pentane
6 C₆H₁₄ CH₃(CH₂)₄CH₃ Hexane
7 C₇H₁₆ CH₃(CH₂)₅CH₃ Heptane
8 C₈H₁₈ CH₃(CH₂)₆CH₃ Octane
9 C₉H₂₀ CH₃(CH₂)₇CH₃ Nonane
10 C₁₀H₂₂ CH₃(CH₂)₈CH₃ Decane

Q8: Are alkanes polar or no-polar molecules?

Answer: Non-polar molecules.

Q9: What are the physical states of Alkane members?

Answer: The first four members, C₁ to C₄ are gases. C₅ to C₁₇ are liquids containing 18 carbon atoms or more solids at room temperature.

Q10: What is the colour and odour of alkanes?

Answer: These are colourless and odourless.

Q11: Boiling point of alkanes ________ with the increase in molecular mass. (Fill in the blanks)

Answer: increases

Q12:  Alkanes can have _________ number of conformations by rotation around C—C single bonds.  (Fill in the blanks)

Answer: infinite

Q13: Alkanes with an even number of carbon atoms have ________ melting points than those with an odd number of carbon atoms due to symmetry. (Fill in the blanks)

Answer: higher

Q14: What type of isomerism is shown by alkanes?

Answer: Alkanes exhibit chain isomerism. 

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