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Chemistry · Grades 9–12

Straight-chain alkanes and names

Use carbon count and the limited scope of the alkane formula.

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Alkane

Acyclic saturated hydrocarbons have only C–C single bonds and formula CₙH₂ₙ₊₂.

Names

The first straight-chain names are methane, ethane, propane, butane, pentane and hexane.

Longest chain

Naming branched examples starts with an appropriate parent chain, not simply the total atom count.

Scope

Rings and multiple bonds change the hydrogen count; do not apply the acyclic formula to them automatically.

Worked examples

What is the name of the straight-chain alkane with three carbons?

The prefix prop- gives three carbons and -ane denotes saturation.

Propane.

How many hydrogens are in an acyclic alkane with five carbons?

2n + 2 = 2 × 5 + 2 = 12.

12

Check your understanding

  1. Which formula matches ethane?

    1. C₂H₆.
    2. C₂H₄.
    3. C₂H₂.

  2. Name the straight-chain alkane CH₃CH₂CH₂CH₃.

  3. How many carbon atoms are in hexane?

Answers and marking notes

Answers and marking notes
  1. C₂H₆.

    An acyclic alkane with n = 2 has 2n + 2 = 6 hydrogens.

  2. butane

    The unbranched chain has four carbon atoms.

  3. 6

    Hex- denotes a six-carbon parent chain.

Further reading and review references

These are reference links, not copied exercises, institutional endorsement or proof of independent review.

Independent educational review required. Grade bands are approximate; these are not officially aligned curricula.