Question

The evaporation of formalin solution leaves a white solid called:
A) Paraformaldehyde
B) Ketone
C) Aldehyde
D) None of the above

Answer 1

Hint: Evaporation is a kind of vaporization process in which solution of water turns from liquid form to vapor form usually at a temperature which is higher than the normal temperature. Evaporation is the natural process in which heat is taken from natural resources.

Complete answer:
Formalin is formed when we add commercial solution of formaldehyde in the water. Chemical formula of formaldehyde is HCHO and of paraformaldehyde is $OH{\left( {C{H_2}O} \right)_n}$ (where $n = 8 - 10$ ). Paraformaldehyde is a polymer which is made up from formaldehyde and chemical properties of paraformaldehyde are the same as formaldehyde because it is made up from it. So, when we evaporate formalin then water molecules are converted from liquid to vapor and we get pure white solid precipitate of paraformaldehyde.

Additional Information: Whenever we evaporate any solution then in that condition the obtained left residue of solid is the pure form of that solid. In the option ketone is given which will not be the right answer because we are evaporating the solution of aldehyde so we never get the solid of ketone.

Note: In this question we have to know about the chemical composition of all the given compounds because as when we didn’t have knowledge about the presence of functional groups and other entities then we are not able to find out the left residue in that solution.