Carbon and its Compounds

Solution

A covalent bond is formed by the sharing of electrons between two atoms to achieve a stable electronic configuration. In methane (CH4), carbon has four valence electrons and needs four more to complete its octet. Hydrogen has one valence electron and needs one more to achieve a duplet. Carbon shares one electron with each of the four hydrogen atoms, resulting in four single covalent bonds. This sharing allows both carbon and hydrogen to achieve stability. Methane is a saturated hydrocarbon with a tetrahedral structure. The bond angle in methane is 109.5 degrees. Covalent bonds are strong and result in low melting and boiling points for covalent compounds. Methane is a colorless, odorless gas used as a fuel. It is the main component of natural gas and biogas. The formation of methane demonstrates the tetravalency of carbon and its ability to form stable compounds through covalent bonding.

Solution

Saturated hydrocarbons are compounds where carbon atoms are connected by single bonds and have the maximum number of hydrogen atoms. Examples include methane (CH4) and ethane (C2H6). Unsaturated hydrocarbons have double or triple bonds between carbon atoms and fewer hydrogen atoms. Examples include ethene (C2H4) with a double bond and ethyne (C2H2) with a triple bond. Saturated hydrocarbons are less reactive due to the presence of single bonds, while unsaturated hydrocarbons are more reactive because of the presence of double or triple bonds. Saturated hydrocarbons undergo substitution reactions, whereas unsaturated hydrocarbons undergo addition reactions. The general formula for saturated hydrocarbons (alkanes) is CnH2n+2, for alkenes (with one double bond) is CnH2n, and for alkynes (with one triple bond) is CnH2n-2. Saturated hydrocarbons are found in natural gas and petroleum, while unsaturated hydrocarbons are used in making plastics and synthetic fibers.

Solution

Combustion is a chemical reaction where a substance reacts with oxygen to produce heat and light. Carbon compounds undergo combustion to form carbon dioxide and water. For example, methane (CH4) burns in oxygen to produce CO2 and H2O: CH4 + 2O2 → CO2 + 2H2O + heat and light. Incomplete combustion occurs when there is insufficient oxygen, producing carbon monoxide (CO) and soot (C). For example: 2CH4 + 3O2 → 2CO + 4H2O. Combustion of hydrocarbons is an exothermic reaction, releasing energy used as fuel. The amount of oxygen available determines the products of combustion. Saturated hydrocarbons burn with a clean blue flame, while unsaturated hydrocarbons burn with a yellow, sooty flame due to incomplete combustion. Combustion is used in engines, stoves, and power plants. It is a major source of energy but also contributes to air pollution.

Solution

Ethanol (C2H5OH) is a colorless liquid with a pleasant smell and burning taste. It is soluble in water and forms hydrogen bonds. Ethanol is used as a solvent in medicines, perfumes, and tinctures. It is the active ingredient in alcoholic beverages. Ethanol reacts with sodium to form sodium ethoxide and hydrogen gas: 2C2H5OH + 2Na → 2C2H5ONa + H2. It undergoes dehydration with concentrated sulfuric acid to form ethene: C2H5OH → C2H4 + H2O at 443K. Ethanol burns with a clean blue flame to produce CO2 and H2O: C2H5OH + 3O2 → 2CO2 + 3H2O + heat. It is used as a fuel in some countries, blended with petrol. Ethanol is also used in hand sanitizers due to its antiseptic properties. Excessive consumption of ethanol leads to health issues like liver damage and addiction. Denatured alcohol is ethanol mixed with methanol to prevent misuse.

Solution

Ethanoic acid (CH3COOH), also known as acetic acid, is a colorless liquid with a pungent smell. It is a weak carboxylic acid and turns blue litmus red. It freezes at 290K, forming glacial acetic acid. Ethanoic acid reacts with bases to form salts: CH3COOH + NaOH → CH3COONa + H2O. It reacts with carbonates and hydrogencarbonates to produce CO2: 2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2. Ethanoic acid undergoes esterification with alcohols to form esters: CH3COOH + C2H5OH → CH3COOC2H5 + H2O. Esters are used in perfumes and flavorings. A 5-8% solution of ethanoic acid in water is called vinegar, used as a preservative and condiment. Ethanoic acid is used in the production of cellulose acetate and synthetic fibers. It is also used in the manufacture of dyes and pharmaceuticals.

Solution

Soaps are sodium or potassium salts of long-chain fatty acids. They are formed by the saponification of fats or oils with NaOH or KOH: Fat + NaOH → Glycerol + Soap. Soaps have a hydrophilic (water-loving) head and a hydrophobic (water-repelling) tail. In water, soap molecules form micelles, trapping oily dirt in the center. The ionic ends of soap interact with water, while the carbon chains interact with oil. Soaps are less effective in hard water due to the formation of insoluble scum (calcium or magnesium salts). Detergents are ammonium or sulfonate salts of long-chain hydrocarbons. They do not form scum in hard water and are more effective cleaners. Detergents are used in shampoos and laundry products. Soaps are biodegradable, while some detergents can cause water pollution. Both soaps and detergents lower the surface tension of water, aiding in cleaning.

Solution

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 covalent bonds. Carbon can form single, double, or triple bonds with other carbon atoms, leading to a variety of structures like straight chains, branched chains, and rings. Catenation allows carbon to form a vast number of compounds, including alkanes, alkenes, alkynes, and aromatic compounds. The ability to form isomers (compounds with the same molecular formula but different structures) further increases diversity. Carbon's tetravalency enables it to bond with other elements like hydrogen, oxygen, nitrogen, and halogens, forming functional groups. These functional groups impart specific properties to carbon compounds. Catenation and tetravalency make carbon the backbone of organic chemistry, leading to millions of known compounds.

Solution

Hydrogenation is the addition of hydrogen to unsaturated hydrocarbons in the presence of a catalyst like nickel or palladium. For example, vegetable oils (unsaturated fats) are hydrogenated to form vanaspati ghee (saturated fats): C2H4 + H2 → C2H6 (in the presence of Ni). The double bonds in unsaturated fats are converted to single bonds, making the fats more solid and stable. Hydrogenation increases the melting point of oils, making them suitable for cooking and baking. However, partially hydrogenated oils contain trans fats, which are harmful to health. Hydrogenation is used in the food industry to produce margarine and shortenings. The process is also used to convert alkenes to alkanes in petroleum refining. Hydrogenation improves the shelf life of oils but reduces their nutritional value.

Solution

Alkanes are saturated hydrocarbons with single bonds between carbon atoms. Their general formula is CnH2n+2. Examples include methane (CH4) and ethane (C2H6). Alkenes are unsaturated hydrocarbons with at least one double bond. Their general formula is CnH2n. Examples include ethene (C2H4) and propene (C3H6). Alkynes are unsaturated hydrocarbons with at least one triple bond. Their general formula is CnH2n-2. Examples include ethyne (C2H2) and propyne (C3H4). Alkanes are less reactive and undergo substitution reactions. Alkenes and alkynes are more reactive and undergo addition reactions. Alkanes burn with a clean blue flame, while alkenes and alkynes burn with a sooty flame. Alkenes and alkynes are used in the production of plastics, synthetic fibers, and chemicals. Alkanes are used as fuels and solvents.

Solution

Functional groups are specific groups of atoms within molecules that determine the chemical properties of those molecules. Examples include hydroxyl (-OH) in alcohols, carboxyl (-COOH) in carboxylic acids, and aldehyde (-CHO) in aldehydes. Functional groups are responsible for the characteristic reactions of organic compounds. For example, alcohols undergo esterification and oxidation, while carboxylic acids react with bases and alcohols. The presence of a functional group can change the physical properties like boiling point and solubility. Functional groups help classify organic compounds into families like alcohols, aldehydes, ketones, and acids. They are crucial in the synthesis of pharmaceuticals, dyes, and polymers. Understanding functional groups allows chemists to predict the behavior of organic compounds and design new molecules for specific applications.

Solution

Catenation is the ability of carbon to form bonds with other carbon atoms, leading to long chains, branched chains, or rings. Tetravalency refers to carbon's ability to form four covalent bonds due to its four valence electrons. Examples include methane (CH4) where carbon forms four single bonds with hydrogen, and ethane (C2H6) where two carbon atoms are bonded together with single bonds.

Solution

Saturated hydrocarbons have single bonds between carbon atoms and are less reactive (e.g., methane, CH4). Unsaturated hydrocarbons have double or triple bonds and are more reactive (e.g., ethene, C2H4, with a double bond). A table can be used to compare their properties, reactivity, and examples.

Solution

In methane, carbon shares its four valence electrons with four hydrogen atoms, each contributing one electron, forming four single covalent bonds. The electron dot structure shows carbon at the center with four hydrogen atoms around it, each connected by a pair of shared electrons.

Solution

Hydrogenation is the addition of hydrogen to unsaturated hydrocarbons in the presence of a catalyst like nickel or palladium, converting them into saturated hydrocarbons. Industrially, it's used to convert vegetable oils into vanaspati ghee by adding hydrogen to the double bonds in the oil molecules.

Solution

Functional groups determine the chemical properties of carbon compounds. For example, alcohols (-OH group) are polar and can form hydrogen bonds, making them soluble in water (e.g., ethanol). Carboxylic acids (-COOH group) are acidic and can donate protons (e.g., acetic acid).

Solution

Soap molecules have a hydrophilic (water-attracting) head and a hydrophobic (oil-attracting) tail. In water, they form micelles where the tails trap oil droplets, and the heads face outward, allowing the oil to be washed away. A diagram would show the micelle structure with oil in the center surrounded by soap molecules.

Solution

Carbon compounds release a large amount of energy upon combustion, making them efficient fuels. They are abundant and can be stored and transported easily. Examples include methane (natural gas) and petrol, which are used for heating and in vehicles.

Solution

Ethanol is a liquid at room temperature with a pleasant smell and is used in alcoholic drinks. Ethanoic acid is a colorless liquid with a pungent smell and is the main component of vinegar. Chemically, ethanol can be oxidized to ethanoic acid, and ethanoic acid reacts with carbonates to release CO2.

Solution

Hard water contains calcium and magnesium ions that react with soap to form insoluble precipitates called scum. This happens because the ions displace sodium or potassium in the soap, forming calcium or magnesium salts that are insoluble in water.

Solution

Structural isomers are compounds with the same molecular formula but different structures. For butane (C4H10), the two isomers are n-butane (a straight chain) and isobutane (a branched chain). Their structures can be drawn showing the arrangement of carbon atoms and hydrogen atoms.

Solution

Catenation allows carbon to form long chains, branched chains, and rings, leading to a vast diversity of compounds. This property, combined with carbon's tetravalency, enables the formation of millions of organic compounds. Examples include linear alkanes like methane (CH4) and complex molecules like DNA. Counterpoints could involve comparing carbon's catenation with other elements like silicon, which forms fewer stable chains.

Solution

Carbon has four valence electrons, making it difficult to gain or lose four electrons to form ions. Sharing electrons through covalent bonding is energetically favorable. For example, methane (CH4) forms four covalent bonds. Ionic bonding would require too much energy to remove four electrons or add four electrons, making it impractical.

Solution

Functional groups like -OH (alcohol), -COOH (carboxylic acid), and -CHO (aldehyde) impart specific chemical properties to organic compounds. For instance, alcohols are polar and can form hydrogen bonds, making them soluble in water. Carboxylic acids are acidic due to the -COOH group. The presence of different functional groups leads to varied reactivity and physical properties.

Solution

Saturated hydrocarbons (alkanes) burn with a clean blue flame, producing CO2 and H2O. Unsaturated hydrocarbons (alkenes and alkynes) burn with a sooty yellow flame due to incomplete combustion, resulting in carbon particles. For example, methane (CH4) burns cleanly, while ethene (C2H4) produces soot. The difference arises from the higher carbon content and double/triple bonds in unsaturated hydrocarbons.

Solution

Homologous series are families of compounds with the same functional group and general formula, differing by a -CH2- unit. They exhibit gradation in physical properties and similar chemical properties. For example, the alcohols methanol (CH3OH), ethanol (C2H5OH), and propanol (C3H7OH) show increasing boiling points but similar reactions. This systematic variation aids in predicting properties and reactions of unknown members.

Solution

Soap molecules have a hydrophilic (water-attracting) head and a hydrophobic (oil-attracting) tail. In water, they form micelles, with tails trapping oily dirt and heads facing outward, emulsifying the dirt. The micelles are washed away with water. For example, stearate ions in soap form micelles around grease. However, soaps are ineffective in hard water due to scum formation with Ca2+ and Mg2+ ions.

Solution

Burning fossil fuels releases CO2, a greenhouse gas, contributing to global warming. It also produces SO2 and NOx, causing acid rain. For example, coal combustion releases sulfur oxides. Counterpoints include the economic necessity of fossil fuels for energy. Alternatives like biofuels and renewable energy can mitigate these impacts.

Solution

Hydrogenation involves adding hydrogen to unsaturated hydrocarbons in the presence of a catalyst (e.g., Ni or Pd). It converts alkenes to alkanes and vegetable oils to solid fats (margarine). For example, ethene (C2H4) becomes ethane (C2H6). This process is crucial in food and chemical industries for producing saturated fats and other products.

Solution

Soaps are sodium/potassium salts of fatty acids, effective in soft water but form scum in hard water. Detergents are sulfonates or ammonium salts, effective in both soft and hard water. For example, sodium stearate (soap) vs. sodium lauryl sulfate (detergent). Detergents are more versatile but can be non-biodegradable, causing environmental issues.

Solution

Ethanol (CH3CH2OH) is formed by fermentation of sugars, while ethanoic acid (CH3COOH) is produced by oxidation of ethanol. Ethanol is a solvent and fuel, whereas ethanoic acid is a weak acid used in vinegar. For example, ethanol reacts with Na to form H2, while ethanoic acid reacts with carbonates to release CO2. Their functional groups (-OH and -COOH) dictate their properties.