Why is it acceptable for propanol to be v/v%, but not ethanol?

Question

Why can we prepare diluted propanol using volume per volume but ethanol using weight per volume?

Answer 1

??? Says who?
When the solute is liquid, of course you can use % (v/v) (or % w/v, whatever you like). You just need to specify it, in order to avoid misunderstandings.
For example, the alcohol content of beverages (which is ethanol) is provided in % (v/v)

Answer 2

Propan-1-ol is a primary alcohol with the formula CH3CH2CH2OH. It is also known as 1-propanol, 1-propyl alcohol, n-propyl alcohol, or simply propanol. It is an isomer of propan-2-ol. It is used as a solvent in the pharmaceutical industry, and for resins and cellulose esters. It is formed naturally in small amounts during many fermentation processes.

1-Propanol is a major constituent of fusel oil, a by-product formed from certain amino acids when potatoes or grains are fermented to produce ethanol. This is no longer a significant source of the material.

1-Propanol is manufactured by catalytic hydrogenation of propionaldehyde. The propionaldehyde is itself produced via the oxo process, by hydroformylation of ethylene using carbon monoxide and hydrogen in the presence of a catalyst such as cobalt octacarbonyl or a rhodium complex.

(1) H2C=CH2 + CO + H2 → CH3CH2CH=O
(2) CH3CH2CH=O + H2 → CH3CH2CH2OH
A traditional laboratory preparation of 1-propanol involves treating 1-iodopropane with moist Ag2O.


ETHANOL:
Ethanol, also known as ethyl alcohol or grain alcohol, is a flammable, colorless, slightly toxic chemical compound with a distinctive perfume-like odor, and is the alcohol found in alcoholic beverages. In common usage, it is often referred to simply as alcohol. Its molecular formula is variously represented as EtOH, CH3CH2OH, C2H5OH or as its empirical formula C2H6O.

Ethanol is produced both as a petrochemical, through the hydration of ethylene, and biologically, by fermenting sugars with yeast.


[edit] Ethylene hydration
Ethanol for use as industrial feedstock is most often made from petrochemical feedstocks, typically by the acid-catalyzed hydration of ethene, represented by the chemical equation

C2H4 + H2O → CH3CH2OH
The catalyst is most commonly phosphoric acid, adsorbed onto a porous support such as diatomaceous earth or charcoal; this catalyst was first used for large-scale ethanol production by the Shell Oil Company in 1947.[1] Solid catalysts, mostly various metal oxides, have also been mentioned in the chemical literature.

In an older process, first practiced on the industrial scale in 1930 by Union Carbide,[2] but now almost entirely obsolete, ethene was hydrated indirectly by reacting it with concentrated sulfuric acid to product ethyl sulfate, which was then hydrolysed to yield ethanol and regenerate the sulfuric acid:

C2H4 + H2SO4 → CH3CH2SO4H
CH3CH2SO4H + H2O → CH3CH2OH + H2SO4