Question

Formalin is 40% aqueous solution of :
A. Methanal
B. Methanoic acid
C. Methanol
D. Methanamine

Answer 1

Hint: An aqueous solution is one in which the solvent is liquid water and an aldehyde is a compound containing a functional group (CHO) with the structure, consisting of a carbonyl center with the a carbon atom is also bonded to hydrogen and to a group, which is any generic alkyl or side chain. Formalin is an aqueous solution of formaldehyde.

Complete answer:
Formaldehyde (systematic name methanal) is a naturally occurring organic compound with the formula \[C{H_2}O{\text{ }}\left( {H - CHO} \right)\]. Formaldehyde is a gas with a boiling point of -21$^\circ$C . It is usually supplied as a stabilized aqueous solution (40% formaldehyde ) known as formalin. When formalin is used as the source of the aldehyde, impurities present generally include water, methanol, formic acid, methyl formate, and carbon dioxide.
Therefore, methanal or formaldehyde is soluble in water, alcohol and ether. Its 40% aqueous solutionIs marketed as formalin.

So the correct option is (A) methanal.

Note: Formaldehyde is more complicated than many simple carbon compounds in that it adopts several different forms. These compounds can often be used interchangeably and can be interconverted.
a) Molecular formaldehyde, a colorless gas with a characteristic pungent, irritating odor.
b) 1,3,5-Trioxane, with the formula \[{\left( {C{H_2}O} \right)_3}\]. It is a white solid that dissolves without degradation in organic solvents. It is a trimer of molecular formaldehyde .