Question

Which of the following has maximum viscosity?
A) Glycol
B) Methanol
C) Kerosene
D) Water

Answer 1

Hint: We know that the greater the number of intermolecular hydrogen bonding the greater the viscosity of the compound. The intermolecular hydrogen bonding increases with an increase in the number of the hydroxyl group \[( - OH)\].

Complete step by step answer:
It is known that viscosity is the measure of resistance to the flow of the liquid.
Generally, viscosity depends upon the two factors:
(1) Intermolecular attractive forces: We know that the greater the intermolecular force of attraction the greater is the viscosity. Hydrogen bonding and the van der Waals forces are strong enough to cause high viscosity. So, we can say that the greater the number of hydroxyl groups greater the hydrogen bonding and hence, greater viscosity.
(2)Temperature: We must be aware that with the rise in temperature, the kinetic energy of the molecules increases. Molecules with greater kinetic energy can easily overcome the intermolecular forces. So, we can say that the viscosity of the liquids decreases with a rise in temperature.
As in the following question, we are not given about the temperature, we will stick with the intermolecular attractive force.
We know that the structure of Glycol contains two hydroxyl groups. So, the intermolecular hydrogen bonding takes place on two sites.
Glycol: \[{\text{HO - C}}{{\text{H}}_{\text{2}}}{\text{ - C}}{{\text{H}}_{\text{2}}}{\text{ - OH}}\]
We also know that water and methanol contain only one site for hydrogen bonding.
Methanol: \[{\text{C}}{{\text{H}}_3}{\text{ - OH}}\]
Water: \[{\text{H - OH}}\]
We know that kerosene is the mixture of hydrocarbons. So, there will be no intermolecular hydrogen bonding.

So, the correct answer is Option A .

Note:
We can get confused that the viscosity is directly proportional to its molecular weight which is wrong. Molecular weight has no relation.