Carbon and its Compounds

A covalent bond is formed when two atoms share one or more pairs of electrons to achieve a stable electron configuration. For example, in a methane molecule (CH4), carbon shares its four valence electrons with four hydrogen atoms. This sharing allows each atom to attain the electron configuration of the nearest noble gas, resulting in a stable molecule.

Carbon forms a large number of compounds due to its ability to catenate (form chains with other carbon atoms) and its tetravalency (ability to form four covalent bonds). These properties allow carbon to form long chains, branched chains, and rings with single, double, or triple bonds, leading to a vast diversity of compounds.

Saturated hydrocarbons have only single bonds between carbon atoms (alkanes), making them less reactive. Unsaturated hydrocarbons have at least one double or triple bond between carbon atoms (alkenes and alkynes), making them more reactive. For example, ethane (C2H6) is saturated, while ethene (C2H4) is unsaturated.

Ethanol and ethanoic acid can be distinguished using sodium carbonate or sodium bicarbonate. Ethanoic acid reacts with these to produce carbon dioxide gas, which turns lime water milky, while ethanol does not react. Additionally, ethanoic acid has a vinegar-like smell, whereas ethanol has a characteristic alcoholic smell.

A homologous series is a group of organic compounds with the same functional group and similar chemical properties, where each successive member differs by a CH2 unit. For example, the alkanes (methane, ethane, propane, etc.) form a homologous series with the general formula CnH2n+2.

Hydrogenation is the addition of hydrogen to unsaturated hydrocarbons in the presence of a catalyst like nickel or palladium. For example, ethene (C2H4) can be hydrogenated to ethane (C2H6). This process is used industrially to convert vegetable oils into solid fats, such as in the production of margarine.

The conversion of ethanol to ethanoic acid involves the addition of oxygen and removal of hydrogen, which defines an oxidation reaction. Ethanol (CH3CH2OH) loses hydrogen and gains oxygen to form ethanoic acid (CH3COOH). This can be achieved using oxidizing agents like alkaline potassium permanganate or acidified potassium dichromate.

Ethanol is a colorless liquid with a pleasant smell and burning taste. It is soluble in water and reacts with sodium to produce hydrogen gas. Ethanol burns with a blue flame to produce carbon dioxide and water. It is used in alcoholic beverages, medicines, and as a solvent in various industries.

Ethanoic acid is a colorless liquid with a pungent vinegar-like smell. It is a weak acid that reacts with carbonates and bicarbonates to produce carbon dioxide. It forms esters with alcohols in the presence of concentrated sulfuric acid. Ethanoic acid is used in the production of vinegar, esters, and other chemicals.

Soap molecules have a hydrophilic (water-attracting) end and a hydrophobic (oil-attracting) end. When soap is added to water, it forms micelles that trap oily dirt in the center, allowing it to be rinsed away. This makes soap effective in cleaning clothes and removing grease and dirt from surfaces.

Hard water contains calcium and magnesium ions that react with soap to form insoluble precipitates called scum. This scum reduces the cleaning efficiency of soap and requires more soap to produce lather. Detergents are preferred in hard water as they do not form scum and remain effective.

Soaps are sodium or potassium salts of long-chain fatty acids, while detergents are sodium salts of sulfonic acids or ammonium salts. Soaps form scum in hard water, whereas detergents do not. Detergents are more effective in hard water and are used in shampoos and laundry products.

Catenation is the ability of carbon atoms to form long chains or rings by bonding with other carbon atoms. This property is due to the strong carbon-carbon bonds and allows carbon to form a vast number of compounds, including straight chains, branched chains, and cyclic structures.

Functional groups are specific groups of atoms within molecules that determine the chemical properties of those molecules. Examples include the hydroxyl group (-OH) in alcohols, the carboxyl group (-COOH) in carboxylic acids, and the aldehyde group (-CHO) in aldehydes. These groups confer characteristic reactions to the compounds.

The electron dot structure of ethene shows two carbon atoms double-bonded to each other, with each carbon atom also bonded to two hydrogen atoms. The double bond consists of four shared electrons (two pairs). This structure can be represented as H2C=CH2, where the lines represent shared electron pairs.

The electron dot structure of ethyne shows two carbon atoms triple-bonded to each other, with each carbon atom also bonded to one hydrogen atom. The triple bond consists of six shared electrons (three pairs). This structure can be represented as HC≡CH, where the lines represent shared electron pairs.

The general formula for alkanes is CnH2n+2, for alkenes is CnH2n, and for alkynes is CnH2n-2. For example, methane (CH4) is an alkane, ethene (C2H4) is an alkene, and ethyne (C2H2) is an alkyne. These formulas help in identifying the type of hydrocarbon.

Carbon is considered versatile because it can form four covalent bonds, allowing it to create a wide variety of structures like chains, branches, and rings. Its ability to catenate and bond with other elements like hydrogen, oxygen, and nitrogen results in millions of organic compounds, making it the basis of life and many industrial materials.

Unsaturated hydrocarbons can be tested using bromine water or Baeyer's reagent. When bromine water is added to an unsaturated compound, it decolorizes due to the addition of bromine across the double or triple bond. Similarly, Baeyer's reagent (alkaline KMnO4) turns from purple to brown when it reacts with unsaturated compounds.

Concentrated sulfuric acid acts as a catalyst and dehydrating agent in the esterification reaction. It speeds up the reaction between a carboxylic acid and an alcohol to form an ester and water. It also removes water produced during the reaction, shifting the equilibrium towards ester formation, thus increasing the yield.

Carbon and its compounds are used as fuels because they release a large amount of heat and light energy when combusted. For example, methane (CH4) burns to produce carbon dioxide and water, releasing energy. Hydrocarbons are abundant, easy to transport, and have high calorific values, making them ideal for various applications.

Diamond and graphite are allotropes of carbon with different structures. Diamond has a rigid 3D network where each carbon is bonded to four others, making it hard and non-conductive. Graphite has layers of carbon atoms bonded to three others, with weak forces between layers, making it soft and a good conductor of electricity.

Carbon is essential in daily life as it forms the basis of all living organisms and many materials we use. It is present in food, clothing, medicines, fuels, and plastics. Carbon compounds like ethanol and ethanoic acid are used in beverages, cleaning agents, and industrial processes, highlighting its versatility and importance.

A soap molecule has a long hydrocarbon chain (hydrophobic tail) that is non-polar and a carboxylate group (hydrophilic head) that is polar. The hydrophobic tail interacts with oils and dirt, while the hydrophilic head interacts with water. This dual nature allows soap to emulsify grease and dirt, enabling their removal with water.

Ethanol reacts with sodium to produce sodium ethoxide and hydrogen gas. The reaction is 2CH3CH2OH + 2Na → 2CH3CH2ONa + H2. This reaction is similar to the reaction of sodium with water but less vigorous, indicating that ethanol is a weaker acid than water.