Solveeit Logo
Login

Question

Question: Which of the following has the lowest boiling point? A. \(2\)-Methylbutane B. \(2\)-Methylpropan...

Which of the following has the lowest boiling point?
A. 22-Methylbutane
B. 22-Methylpropane
C. 2,22,2-Dimethylpropane
D. n-pentane

Explanation

Solution

We know that in thermodynamics, depending on the pressure applied, the boiling point of a liquid varies; the normal boiling point is the temperature at which the vapour pressure is equal to the normal air pressure at sea level. A substance's boiling point is the temperature at which a liquid's vapour pressure equals the pressure surrounding the liquid, and the liquid transforms into a vapour. A liquid's boiling point varies depending on the ambient pressure surrounding it.
With increase in molecular mass, the boiling point increases-ΔTbαm\Delta {T_b}\alpha m

Complete step by step answer:
We have studied the significant knowledge about the physical properties and structural characteristics of various compounds which can be given by the boiling point of organic compounds. The boiling point helps define a compound and describe it. When the vapour pressure equals the ambient pressure, a liquid boils. Vapour pressure is measured by a molecule's kinetic energy.
We must understand that the usual boiling point of a compound is a measure of that compound's volatility. The higher the boiling point, the compound is less volatile. Conversely, the lower the boiling point, the compound is more highly volatile. At a given temperature, if the normal boiling point of a compound is lower, then that compound will normally exist at atmospheric pressure as a gas. If the compound's boiling point is higher, it then exists as a liquid or a solid.
With rising molecular mass, the boiling point increases. Through an increase in branching, for compounds with the same molecular mass, the boiling point decreases.
Molecular mass of 22-Methylbutane: 72gmol −172gmol{{\text{ }}^{ - 1}}
Molecular mass of 22-Methylpropane: 58gmol −158gmol{{\text{ }}^{ - 1}}
Molecular mass of 2,22,2 -Dimethylpropane: 72gmol −172gmol{{\text{ }}^{ - 1}}
Molecular mass 22-Methylbutane: 72gmol −172gmol{{\text{ }}^{ - 1}}
Molecular mass of n-pentane: 72gmol −172gmol{{\text{ }}^{ - 1}}
Of all the compounds given above, 22-methylpropane has the lowest molecular mass. Thus, 22-methylpropane has the lowest boiling point.
Option B is the correct option as22-Methylpropane has the lowest boiling point.

So, the correct answer is Option B.

Note: We know that pentane, an alkane with five carbon atoms, is an organic compound with the C5H12{C_5}{H_{12}}formula. The word can refer to any or a combination of three structural isomers: pentane, however, means exclusively the n-pentane isomer in the IUPAC nomenclature; the other two are called isopentane and neopentane. 22-Methylbutane is used as a solvent, is a building block chemical used to shape other industrial sub-positions in reactions, and has been used to produce chlorinated compounds and to produce amyl-naphthalene and isoprene.