Question:

But-2-yne is reacted separately with one mole of Hydrogen as shown below: 

 

A. A is more soluble than B
B. B The boiling point & melting point of $A$ are higher and lower than $B$ respectively 
C. A is more polar than $B$ because dipole moment of $A$ is zero 
D. $Br _2$ adds easily to $B$ than $A$ 
Identify the incorrect statements from the options given below:

Updated On: Jan 14, 2025
  • A, C & D only

  • A and B only
  • B, C & D only

  • B and C only
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The Correct Option is C

Solution and Explanation

Properties of Alkenes:

  • Melting Point: The melting point of trans alkene is greater than that of cis alkene due to the higher symmetry of trans isomers, which allows better packing in the solid state.
  • Boiling Point: The boiling point of cis alkene is greater than that of trans alkene due to stronger intermolecular forces, as cis isomers are more polar.
  • Bromine Addition: Bromine (Br2) adds more easily to cis alkene than trans alkene because of the closer proximity of substituents in cis isomers.
  • Isomers: A is cis–but–2–ene, and B is trans–but–2–ene.
  • Solubility: A (cis–but–2–ene) is more soluble due to its polarity, as cis isomers have a net dipole moment.

The correct answer is option (C): B, C & D only

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Concepts Used:

Dihydrogen

Dihydrogen is the homonuclear diatomic molecule built from two hydrogen atoms. This molecule characterizes a covalent bond between two hydrogen atoms, satisfying each of their required pair configurations.

Structure of Dihydrogen:

The dihydrogen molecule characterizes a single covalent bond between the two hydrogen atoms that comprise it. This molecule has a linear shape and is nonionic in nature. Each hydrogen atom comes up with one electron towards the covalent bond.

Properties of Dihydrogen:

  • At Standard Temperature and Pressure (STP), dihydrogen exists in the gaseous state.
  • The melting point of H2 is 13.99 Kelvin. Transforming this value to the celsius scale, the melting point of dihydrogen can be expressed as -259.16 degrees celsius.
  • The boiling point correlated with dihydrogen corresponds to 20.271 on the Kelvins scale. Transforming this value into the celsius scale, the boiling point of H2 can be represented as -252.879 degrees celsius.
  • The latent heat of fusion associated with the H2 molecule correlates to 0.117 kilojoules per mole.
  • The latent heat of vaporization (also known as the enthalpy of vaporization) of dihydrogen is equivalent to 0.904 kilojoules per mole.