Final answer:
The given alkane molecular formulas C3H8, C6H14, CH4, and C8H18 are named propane, hexane, methane, and octane, respectively, according to the number of carbon atoms they contain.
Step-by-step explanation:
The names of the straight-chain alkanes with the given molecular formulas are as follows:
- C3H8 is called propane.
- C6H14 is called hexane.
- CH4 is called methane.
- C8H18 is called octane.
These names are derived from the number of carbon atoms in the chain, followed by the suffix -ane to indicate that they are alkanes. The meth-, eth-, prop-, and corresponding prefixes denote one, two, three, and so on carbon atoms respectively.