<span>It generally does not mean that there is double the oxygen, but in this case there is double, because the subscript number tells how many atoms of that element are in a particle. In this case, there are two of the oxygen, hence the DI-oxide verbiage, and one of the carbon. When there is only one, it's MONOxide, to indicate only one atom.</span>
Answer:
The heat of vaporisation of methanol is "3.48 KJ/Mol"
Explanation:
The amount of heat energy required to convert or transform 1 gram of liquid to vapour is called heat of vaporisation
When 8.7 KJ of heat energy is required to vaporize 2.5 mol of liquid methanol.
Hence, for 1 mol of liquid methanol, amount of heat energy required to evaporate the methanol is = 
= 3.48 KJ
So, the heat of vaporization 
Therefore, the heat of vaporization of methanol is 3.48KJ/Mol