Question

Propane is:

• A. \( \mathrm{CH_3 - CH_2 - CH_3} \)
• B. \[ \mathrm{ CH_3 - CH - CH_3 \quad \Bigg( \begin{array}{c} \phantom{CH_3}
  CH_3 \end{array} \Bigg) } \]
• C. \[ \mathrm{ CH_3 - C - CH_3 \quad \Bigg( \begin{array}{c} \phantom{CH_3}
  CH_3 \end{array} \Bigg) } \]
• D. \( \mathrm{(CH_3)_2CH - CH_2 - CH_3} \)

Hint:

Straight-chain alkanes follow the general formula \( \mathrm{C_nH_{2n+2}} \). Propane is the third member with 3 carbon atoms: \( \mathrm{CH_3 - CH_2 - CH_3} \).

Answer 1

The Correct Option is A

Propane is a member of the alkane family, which are saturated hydrocarbons containing only single bonds between carbon atoms. Alkanes follow the general molecular formula \( \mathrm{C_nH_{2n+2}} \), where \( n \) is the number of carbon atoms. For propane, \( n = 3 \), so its molecular formula is: \[ \mathrm{C_3H_8} \] \smallskip 1.
Molecular Structure of Propane:

Propane consists of three carbon atoms connected in a straight, unbranched chain.
Each carbon atom forms four covalent bonds to satisfy the octet rule. In propane:

The two end carbon atoms are bonded to three hydrogen atoms each.
The middle carbon atom is bonded to two hydrogen atoms.

The structural formula can be written as: \[ \mathrm{CH_3 - CH_2 - CH_3} \] This represents a continuous chain with all carbon atoms bonded by single bonds (sigma bonds).
\smallskip 2.
Properties of Propane:

Being a saturated hydrocarbon, propane is relatively chemically stable but will undergo combustion to produce carbon dioxide and water.
Propane is a gas at room temperature and pressure but can be easily liquefied under moderate pressure, making it a convenient fuel source.
It is widely used as a fuel for heating, cooking, and as an energy source in engines (for example, in LPG—liquefied petroleum gas).
\smallskip 3.
Comparison with Other Options:

Other given options might include branched alkanes, such as isobutane (\( \mathrm{C_4H_{10}} \)), where the carbon atoms form a branched structure instead of a straight chain.
Branched alkanes differ in physical properties such as boiling points and melting points due to the shape and surface area differences.
The straight-chain structure of propane is the simplest form of alkane with three carbon atoms, without any branches.
\smallskip 4.
Significance of the Straight-Chain Structure:

The linear structure leads to predictable physical properties such as boiling and melting points, which are important for industrial applications.
The shape and bonding also influence reactivity patterns; for example, straight-chain alkanes generally undergo substitution reactions under specific conditions.
\smallskip In conclusion, propane is a simple, straight-chain alkane with three carbon atoms and the molecular formula \( \mathrm{C_3H_8} \). Its structure \( \mathrm{CH_3 - CH_2 - CH_3} \) distinguishes it from branched alkanes or other hydrocarbons, and it plays an important role as a commonly used fuel due to its physical and chemical properties.