Bond length is inversely proportional to bond order. Ethane contains a single carbon-carbon bond (sp3-sp3 hybridization), which is the longest. Ethene has a double bond (sp2-sp2), and ethyne has a triple bond (sp-sp), both of which are shorter due to increased s-character and electron density between the nuclei. Benzene exhibits intermediate bond lengths due to resonance.

Methane (CH4) consists of one central carbon atom bonded to four hydrogen atoms. Each carbon-hydrogen bond is a single covalent bond formed by the overlap of the carbon's sp3 hybridized orbital with the 1s orbital of a hydrogen atom. Therefore, there are exactly four single bonds in the molecule.

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Isomorphic substances are those that have the same chemical composition but differ in their physical properties, such as crystal shape or color, and also exhibit different chemical properties.

Buckyballs, also known as buckminsterfullerene, is a type of carbon molecule that is composed of 60 carbon atoms arranged in a spherical shape. It is an allotrope of carbon, which means it has a different arrangement of atoms than other forms of carbon, such as graphite or diamond.

Grignard reagents react with water to produce hydrocarbons. This reaction is a common method for forming carbon-carbon bonds.

The Lucas reagent reacts fastest with tertiary alcohols. Among the options, (CH3)3COH is a tertiary alcohol, which reacts rapidly with the Lucas reagent to form a chloroalkane.

Oxidation of a secondary alcohol forms a ketone, as the reaction targets the carbon with two alkyl groups, creating a carbonyl group.

When aldehydes are heated with Fehlings solution, a precipitate forms. This precipitate is characterized by its color. Among the given options, 'brick red' is the correct answer. The reaction involves the oxidation of aldehydes to their corresponding carboxylic acids, which forms a complex copper(II) ion with the Fehling's reagent. The resulting color is brick red.

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