Question

Formalin is the commercial name of
A. Formic acid
B. Fluoroform
C. $40\%$ aqueous solution of methanol
D. Paraformaldehyde

Answer 1

Formaldehyde is the simplest aldehyde made of hydrogen, carbon and oxygen. It is one of a large family of chemicals known as volatile organic compounds which evaporates and becomes gaseous at room temperature.

Complete step by step answer:
Formaldehyde also known as methanal is a reactive molecule and first in the series of aliphatic aldehydes. Its chemical formula is $C{H_2}O$. Its structure is a shown:

However, it is formed primarily by methanol vapor-phase oxidation, and is commonly sold as formalin, an aqueous solution of $40\%$ methanal. So, a saturated water solution of about $40\%$ formaldehyde by volume or $37\%$ by mass, is called formalin. Since, $100\%$formalin contains up to $15\%$ of methanol as a stabilizer, it has a significant impact on cell fixation.
Moreover, formaldehyde reacts with a base like sodium hydroxide and forms sodium formate and methanol. The reaction is as shown:
$2HCHO + NaOH \to HCOONa + C{H_3}OH$
It also reacts with ammonia and forms formamidine and water. The chemical equation is as shown:
$6HCHO + 4N{H_3} \to (C{H_2})6{N_4} + 6{H_2}O$

Hence, option C is correct.

Note:
Formalin is commonly used as an industrial disinfectant, and as a preservative in funeral homes and medical labs. It can also be used as a preservative in some foods and in products such as antiseptics, medicines and cosmetics. It is also used as an adulterant in milk to increase its shelf life for long distance transportation without refrigeration.