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Question
Answer the following question.
What is methane? Draw its electron dot structure. Name the type of bonds formed in this compound. Why are such compounds:
(i) poor conductors of electricity? and
(ii) have low melting and boiling points? What happens when this compound burns in oxygen?
Solution
Methane is a colorless, odorless, and highly flammable gas which is the main component of natural gas. It is also called as marsh gas as it is produced when vegetation decomposes naturally in any swampy or marshlands.
Electron Dot structure of methane is:
The type of bonds present in methane is all covalent bonds between four hydrogen atoms and the single carbon atom at the center of the molecule.
- Methane is a poor conductor of electricity because in methane all bonds are covalent bonds and therefore no free electrons are present in the molecule that can help in the conduction of electricity.
- Covalent compounds have low intermolecular forces of attraction between the molecules and thus show low melting and boiling points. Since methane is also a covalent compound thus methane has very low melting and low boiling point. When methane is burned in the presence of Oxygen it forms Carbon dioxide gas and water as a product of the reaction.
\[\ce{\underset{\text{Methane}}{CH4} +\underset{\text{Water}}{O2} -> \underset{\text{Carbon dioxide}}{CO2}+\underset{\text{Water}}{H2O}}\]
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Alkane
Complete the following activity.
Write the names of the hydrocarbons for the following structural formula.
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| \[\begin{array}{cc}\phantom{......}\ce{H}\phantom{...}\ce{H}\phantom{...}\ce{H}\phantom{..}\\ \phantom{.....}|\phantom{....}|\phantom{....}|\\ \ce{H - C - C = C}\\\phantom{.....}|\phantom{.........}|\\ \phantom{.....}\ce{H}\phantom{........}\ce{H}\end{array}\] |
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Which of the following are correct structural isomers of butane?
- \[\begin{array}{cc}
\ce{H}\phantom{...}\ce{H}\phantom{...}\ce{H}\phantom{...}\ce{H}\\
|\phantom{....}|\phantom{....}|\phantom{....}|\\
\ce{H - C - C - C - C - H}\\
|\phantom{....}|\phantom{....}|\phantom{....}|\\
\ce{H}\phantom{...}\ce{H}\phantom{...}\ce{H}\phantom{...}\ce{H}\\
\end{array}\] - \[\begin{array}{cc}
\ce{H}\phantom{...}\ce{H}\phantom{...}\ce{H}\\
|\phantom{....}|\phantom{....}|\\
\ce{H - C - C - C - H}\\
|\phantom{.....}|\phantom{.....}|\\
\ce{H}\ce{H-C-H}\ce{H}\\
|\\
\ce{H}\\
\end{array}\] - \[\begin{array}{cc}
\ce{H}\phantom{...}\ce{H}\phantom{...}\ce{H}\\
|\phantom{....}|\phantom{....}|\\
\ce{H - C - C - C - H}\\
|\phantom{.....}\backslash\phantom{..}|\\
\phantom{....}\ce{H}\phantom{......}\ce{C - H}\phantom{}\\
\phantom{.......}|\\
\phantom{.......}\ce{H}\\
\end{array}\] - \[\begin{array}{cc}
\ce{H}\phantom{...}\ce{H}\\
|\phantom{....}|\\
\ce{H - C - C - H}\\
|\phantom{....}|\\
\ce{H - C - C - H}\\
|\phantom{....}|\\
\ce{H}\phantom{...}\ce{H}\\
\end{array}\]
The table shows the electronic structures of four elements.
| Element | Electronic Structure |
| P | 2, 6 |
| Q | 2, 8, 1 |
| R | 2, 8, 7 |
| S | 2, 8, 8 |
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