Atmospheric pressure decreases as altitude increases. In other words, there is more air pushing down on you at sea level, and there is less air pressure pushing down on you when you are on a mountain. If hexane (C6H14C6H14), octane (C8H18C8H18), and octanol (C8H17OHC8H17OH) are heated evenly at different altitudes, rank them according to the order in which you would expect them to begin boiling.
A) Hexane at high altitude. B) Octane at high altitude. C) Octane at sea level. D) Octanol at sea level.

Octanol at sea level> Octane at sea level > Octane at high altitude > Hexane at high altitude

Explanation:

Let us have it behind our minds that the boiling points of alkanes depends on the length of the alkyl chain. The longer the chain length, the higher the boiling point of the alkane.

Also, octanol has hydrogen bonding between its molecules in addition to dispersion forces, hence it has a higher boiling point than octane and hexane at sea level.

So, the order of boiling points required at the specified altitudes is;

Octanol at sea level> Octane at sea level > Octane at high altitude > Hexane at high altitude

the correct option is c.

isotopes refers to different forms of the same element with the same atomic number but different mass number as a result of difference in their neutron numbers. isotopes have different relative atomic mass but share the same chemical properties.