Carbon and its Compounds RRB PYQ MCQ

Both the statements are correct. Statement-I correctly identifies that carbon has a unique ability to form bonds with other carbon atoms, leading to the creation of large and complex molecules. Statement-II explains this property, known as catenation, where an element can bond with itself to form chains, rings, or networks. This characteristic is fundamental to carbon's versatility in forming various organic compounds.

Carbon forms strong bonds due to its small atomic size, which allows the atoms to come close together, enabling the formation of stable covalent bonds. This property supports carbon's ability to form large, complex molecules, a feature known as catenation.

The correct answer is C3H7OH → Propanol → Propyl alcohol. Propanol, also known as propyl alcohol, is an alcohol with the molecular formula C3H8O. It exists in two isomeric forms: 1-propanol (or n-propanol) and 2-propanol (isopropanol).

The reaction provided is the oxidation of ethanol CH3CH2OH using strong oxidizing agents (alkaline potassium permanganate or acidified potassium dichromate and heat). Ethanoic acid (CH3COOH) is produced in the reaction. Ethanol is a primary alcohol with two carbon atoms while alkaline potassium or acidified potassium dichromate act as strong oxidising agents. Strong oxidation of a primary alcohol yields a carboxylic acid with the same number of carbon atoms.

Cyclohexane, with the molecular formula C6H12, has 6 carbon-carbon (C-C) bonds and 12 carbon-hydrogen (C-H) bonds, resulting in a total of 18 covalent bonds. Each of the six carbon atoms is bonded to two neighbouring carbon atoms (forming 6 C-C bonds) and two hydrogen atoms (forming 12 C-H bonds), giving a total of 18 covalent bonds in the molecule.

Unsaturated hydrocarbons have a higher carbon-to-hydrogen ratio compared to saturated ones. During combustion, there isn't enough oxygen in the air to burn all the carbon completely. This incomplete combustion produces unburnt carbon particles, which glow yellow and appear as black smoke. Saturated hydrocarbons typically produce a clean blue flame due to their lower carbon-to-hydrogen ratio and a higher percentage of hydrogen.

2-ethyl pentane is not a possible isomer of hexane. Hexane (C6H14) has several isomers, including n-hexane, 2-methylpentane, 3-methyl pentane, 2,2-dimethyl butane, and 2,3-dimethyl butane. However, 2-ethyl pentane is not a valid isomer because it implies a seven-carbon chain, which does not align with the molecular formula of hexane (C6H14).

Catenation is the unique property of an element to form long chains or rings by bonding with atoms of the same element. In carbon, this 'self-linking' ability is exceptionally strong, allowing it to create stable, complex backbones for millions of different organic compounds. Unlike other elements, the bond between two carbon atoms is very strong and stable. This means the chains don't easily fall apart, allowing for the formation of long straight chains, branched structures, and closed rings. Because carbon can keep adding to itself, it can form anything from a simple two-carbon gas (ethane) to massive, complex structures like DNA or synthetic plastics. While catenation provides the backbone, carbon's tetravalency allows other elements like hydrogen, oxygen, and nitrogen to 'plug in' to that backbone, creating the vast variety of substances we see in biology and chemistry.

The compounds C3H8, C4H10, and C5H12 all belong to the same homologous series of alkanes, which follow the general formula CnH2n+2. A homologous series consists of compounds with similar chemical properties and a gradual change in physical properties. Each subsequent compound in this series differs by one CH2 unit.

A blue, non-luminous flame seen when a hydrocarbon is burnt indicates complete combustion with high temperature.