Question

The Society of Automotive Engineers has established an accepted numerical scale to measure the viscosity of motor oil. For example, SAE 40 motor oil has a higher viscosity than an SAE 10 oil. Rank the following hydrocarbons by their expected viscosity. Rank from most to least viscous. To rank items as equivalent, overlap them.
a. CH3CH2CH2CH2CH2CH3 b. CH3CH2CH2CH2CH2CH2CH2CH3 c. CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

Answer 1

Answer:

Most viscous to least viscous: $(c)> (b)> (a)$

Explanation:

For hydrocarbons, viscosity increases with increasing molar mass. Because increasing molar mass signifies increase in number of electrons in molecules.

We know that in non-polar hydrocarbons, only van der waal intermolecular force exists. Van der waal force is proportional to number of electrons in a molecule.

Therefore with increasing molar mass, van der waal force increases. hence molecules gets more tightly bind with each other resulting increase in viscosity.

Here molar mass order : $(c)> (b)> (a)$

Therefore viscosity order : $(c)> (b)> (a)$