The first member of the alkyne group of hydrocarbons is
- A.propyne
- B.ethyne
- C.methyne
- D.butyne
Correct answer
Explanation
The correct answer is B, ethyne. An alkyne contains a carbon to carbon triple bond, which needs at least two carbon atoms, so the series begins with ethyne, C2H2, also called acetylene and used with oxygen in welding. Option A is wrong because propyne, with three carbon atoms, is the second member of the series, not the first. Option C is wrong because a compound called methyne cannot exist as an alkyne at all: methane has a single carbon atom and there is no second carbon for it to form a triple bond with, which is exactly the trap the option is meant to spring. Option D is wrong because butyne has four carbon atoms and is the third member. The general formula of the series is CnH2n-2, and putting n equal to two gives C2H2, confirming ethyne as the first member.
Read the full article: Carbon and Its Compounds: Bonding, Allotropes and PYQs
Practice Questions
View allCooking gas (LPG) mainly consists of
- A.Ethene
- B.Ethyne
- C.Propene
- D.Propane and Butane
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Liquefied petroleum gas is a mixture of these two saturated hydrocarbons, which are gases at ordinary pressure but turn liquid under moderate pressure, so a large quantity of fuel fits into a small cylinder; a strong-smelling compound is added so that a leak is noticed.
Read the full explanation →How many isomers does C6H14 have?
- A.3
- B.6
- C.4
- D.5
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Hexane, C6H14, can be drawn as a straight chain of six carbons, as two chains of five carbons with a methyl branch in different positions, and as two chains of four carbons carrying branches, which gives five different structures with the same molecular formula.
Read the full explanation →Compounds with exactly two double carbon to carbon bonds are known as ______.
- A.Terpenes
- B.Dienes
- C.Trialkyne
- D.Dialkyne
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The prefix di stands for two and the ending ene for a carbon to carbon double bond, so a diene is a hydrocarbon carrying exactly two such bonds; buta-1,3-diene, the raw material of synthetic rubber, is the standard example.
Read the full explanation →A gas stove flame burns blue because of
- A.Complete combustion of fuel
- B.Presence of hydrogen in the air
- C.Hazardous combustion
- D.Insufficient oxygen
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When enough air reaches the burner, every carbon atom of the fuel is oxidised fully to carbon dioxide and the flame is blue and hot, giving the maximum heat for the gas consumed.
Read the full explanation →The ability of carbon atoms to link with one another to form long chains and rings is called
- A.Tetravalency
- B.Catenation
- C.Isomerism
- D.Allotropy
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Catenation is the self-linking of atoms of the same element, and carbon shows it more strongly than any other element because the carbon to carbon bond is short and exceptionally strong, which is why chains of many carbon atoms remain stable.
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