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The correct option is (b) insoluble, INCREASE

For explanation: Alkynes are insoluble in WATER but SOLUBLE in organic solvents like ethers, carbon tetrachloride and Benzene. The melting point, boiling point and density of alkynes increase with the increase in the molar MASS.

Correct option is (B) paraffin

The BEST explanation: Alkanes are SATURATED aliphatic open chain hydrocarbons with carbon-carbon single BONDS. They are inert under normal conditions they do not react with ACIDS, bases and other reagents. They were earlier known as paraffin, in Latin Param = little and affine means affinity.

The correct answer is (b) oxalic acid

The best explanation: When one MOLE of ethane reacts with ALCOHOLIC KMNO4 1 mole of oxalic acid is formed, when it reacts with acidic KMnO4 two moles of FORMIC acid are formed and when it reacts with K2Cr2O7 one mole of Acetic acid is formed.

The correct CHOICE is (d) both electrophilic and nucleophilic addition

To elaborate: ALKYNES show electrophilic as well as nucleophilic addition reactions. Electrophilic addition reactions FOLLOW the markownikoff RULE, various examples for these reactions are the addition of DIHYDROGEN, halogens, water and hydrogen halides.

The correct answer is (B) Skew

To explain I would say: The intermediate conformation between ECLIPSED and staggered is known as skew and gauche formations. The eclipsed FORM is least stable but the staggered form is the most stable DUE to the greater DISTANCE between the bond pairs or lesser torsional strain.

Correct answer is (b) n-Octane is greater than ISOOCTANE

For explanation I would say: The boiling POINT of ALKANES decreases on branching and boiling point is directly proportional to the van der walls forces and the van der wall forces are directly proportional to the molecular mass as well as SURFACE area. So we can say that the boiling point of n-Octane is greater than that of isooctane.

Correct answer is (c) one CARBON less

To explain I would say: Decarboxylation of sodium or potassium salt of fatty acids is decarboxylation reaction. This reaction is used for DESCENDING of series as the alkane obtained has one carbon less than the parent compound. Here QUICKLIME is used as it is more hygroscopic than sodium hydroxide and KEEPS Sodium Hydroxide in a DRY state.

Correct option is (d) Wurtz reaction

To explain: Wurtz reaction is used to increase the LENGTH of the carbon chain, Kolbe’s electrolysis is used when alkanes require EVEN number of carbon ATOMS while clemmensen reduction and wolff-kishner are used for removing water MOLECULE.

The correct choice is (d) 3.5

To EXPLAIN I WOULD say: The combustion reaction of alkanes has a standard reaction that is CnH2n+2 + (3n/2 + 1/2)O2 → nCO2 + (N + 1)H2O. In the case of combustion of ethane, n = 2. That means the number of moles of oxygen REQUIRED is 3(2)/2 + 1/2 = 3.5

Right option is (b) nonpolar, colourless

The best I can explain: Alkanes being nonpolar in nature, soluble in nonpolar solvents but insoluble and polar solvent such as WATER. The first four members of alkanes are colourless gases, the NEXT 13 members are colourless liquids and next HIGHER members are colourless solids, this can be explained on the basis of the MAGNITUDE of attraction forces.

The correct answer is (B) Benzene hexachloride

To explain: Under ultra-violet light, three chlorine MOLECULES add to benzene to PRODUCE benzene hexachloride. It is also known as gammaxene. Its chemical FORMULA is C6H6Cl6and undergoes ADDITION reaction.

Correct option is (b) False

To explain I would say: ALKENES are unsaturated noncyclic hydrocarbons which have sp^2 HYBRIDIZATION with 120-degree bond angle. They are called olefins which MEAN oil forming and it indicates they are highly reactive NATURE alkynes general FORMULA is CnH2n.

The correct CHOICE is (c) both GEOMETRICAL and STRUCTURAL

The explanation is: Alkynes show both structural isomerism as well as geometrical isomerism, structural isomerism EXHIBITED by ALKENES are chain isomerism and position isomerism, while alkenes also exhibit stereoisomerism as geometrical cis-trans isomerism.

The correct option is (d) dehydrohalogenation

The best I can explain: When chloroethane is heated in the presence of ALCOHOLIC potassium Hydroxide, a beta-elimination product is FORMED, that is ethane, hydrogen, and CHLORINE are REMOVED which is dehydrohalogenation (the HALOGEN can be either chlorine or bromine or iodine).

Right CHOICE is (a) Yes

The best EXPLANATION: Yes, when ethyne reacts with arsenic trichloride in presence of anhydrous aluminium trichloride, it forms 2 CHLORO vinyl arsonous dichloride, it is also known as LEWISITE, which is a poisonous gas. So we can say that alkynes do react with arsenic trichloride.

The correct option is (b) markovnikov’s rule

Easy explanation: According to markovnikov’s rule the negative part of the ADDENDUM which means adding molecule, GETS attached to that carbon atom which possesses LESS number of HYDROGEN atoms, it’s the opposite of ANTI markovnikov’s rule.

The correct choice is (B) 3

To elaborate: Corey-House synthesis is ONE of the methods of preparation of ALKANES and this method can be used to prepare alkanes having an odd number of carbon atoms. As 6, 2, and 4 are even numbers only the COMPOUND with three carbon atoms can be prepared.

Correct choice is (b) False

For EXPLANATION I would say: Aromatic hydrocarbons are non-polar MOLECULES. Nonpolar solvents DISSOLVES nonpolar molecules as ‘like’ dissolves ‘like’. HENCE aromatic hydrocarbons are immiscible with water but are readily miscible with ORGANIC solvents.

Correct choice is (a) formic acid

Best explanation: When a mole of ethane is SUBJECTED to ozonolysis, it REACTS with a mole of ozone in presence of carbon tetrachloride and zinc or water, in order to give ONE mole GLYOXAL and then it forms TWO moles formic acid.

The correct option is (b) Peroxide effect

Easy EXPLANATION: Anti markownikoff RULE is also KNOWN as peroxide effect and kharash effect; in the presence of ORGANIC peroxide, the addition of only hydrogen Bromide molecule on unsymmetrical ALKENE, takes place contrary to the markovnikov rule.

Right CHOICE is (b) Hexachlorobenzene

Easiest explanation: If EXCESS of electrophilic reagent is used, substitution reaction may take place in which other hydrogen atoms of benzene ring may ALSO be successively replaced by electrophile. Benzene on TREATMENT with excess of chlorine in the presence of anhydrous ALCL3 can be chlorinated to hexachlorobenzene.

Right choice is (B) dependent

To elaborate: Ease of HYDROGENATION depends on the steric crowding across multiple Bond, more the steric crowding, the less is REACTIVITY towards hydrogenation. This concept is USED in one of the methods of preparation of alkanes from the hydrogenation of alkenes and alkynes.

Correct option is (d) An aqueous solution of potassium PERMANGANATE

Best EXPLANATION: The DILUTE aqueous solution of potassium permanganate is known as BAYER’s reagent. ALKENES decolorize Bayer’s reagent and it is used as a test for unsaturation in alkenes. It is a powerful oxidant as well as a syn-reaction occurs.

Right CHOICE is (a) -CHO

Best explanation: The groups which direct the INCOMING group to meta position are called meta directing groups. Some examples are -CHO,-COR, -COOH, -CN. The overall electron density on BENZENE ring decreases. Hence, they are called deactivating groups.

The correct answer is (c) Alkyne

For explanation I would say: The acidic behavior depends upon the HYBRIDIZATION of the molecule as we know that alkane has SP3 hybridization, alkane has SP^2 hybridization and alkynes has sp hybridization, due to the higher percentage of s-character, alkyne becomes HIGHLY acidic when compared with alkene and alkane.

The correct option is (a) true

To elaborate: Calcium carbonate is heated and results in the formation of calcium oxide and carbon dioxide and then calcium oxide combines with carbon in ORDER to form calcium carbide and carbon monoxide, when calcium carbide combines with water it forms calcium hydroxide as WELL as an ALKYNE that is ETHYNE C2H2.

The CORRECT choice is (c) Friedel-Crafts alkylation reaction

The explanation is: Aluminum chloride reacts with methyl chloride to form an electrophile. This electrophile attacks the π electron to form carbocation. As a result, alkylbenzene is FORMED along with HCL as product.

The correct option is (b) No

Explanation: The alkynes EXHIBIT electrophilic addition reaction, they are less reactive when compared with ALKENES and this is due to the dissociation of π-electron cloud REQUIRES more energy comparatively. So we can SAY that they are not more reactive when compared to alkenes.

Correct option is (C) differ in a few aspects

The best explanation: Alkenes as a class resemble ALKANES in physical properties, except in types of isomerism and DIFFERENCE in polar nature. The first three of the series are gases, the next 14 are liquid and the higher MEMBERS are solids they show a regular increase in boiling POINT with an increase in size.

Correct answer is (d) 12 σ and 3 π

The BEST explanation: Sigma bonds are the strongest TYPE of covalent bond, formed by head-on overlapping. In benzene, there are 6(C-C) σ bonds and 6(C-H) σ bonds. Pi bonds are formed by LATERAL overlapping of atomic ORBITALS. There are totally 3(C=C) π bonds.

Correct option is (d) Hydrogen BROMIDE is less than that of hydrogen iodide

The best I can EXPLAIN: In CHEMICAL properties of alkenes, HCL, hydrogen Bromide and hydrogen iodide are added to alkenes to form alkyl HALIDES as PER their reactivity order that is; hydrogen iodide’s reactivity is greater than that of hydrogen Bromide and it is greater than that of HCL.

The correct choice is (a) High temperature, High pressure, NICKEL catalyst

The explanation is: Benzene NORMALLY does not undergo addition reactions, but under DRASTIC conditions, i.e. at high temperature (473 – 523K)and high pressure in the presence of nickel catalyst, hydrogenation of benzene gives cyclohexane.

The correct option is (c) 873 Kelvin

To explain I would say: An EXAMPLE of cyclic polymerization of an alkyne is given by; when 3 moles of ethane is at 873 Kelvin in presence of RED hot iron TUBE they POLYMERISE in a cyclic form in ORDER to form Benzene a six-membered ring with alternate double bonds.

The correct answer is (a) CnH2n-2

The explanation: Alkynes are UNSATURATED hydrocarbons with the general FORMULA of CnH2n-2. Few examples are ethyne (PUT n = 2 in the general formula) C2H2, propyne (put n = 3 in the general formula) C3H4, butyne (put n = 4 in the general formula) C4H6 etc.