Question

Anhydrous formic acid is prepared by:
A) heating $NaOH$with$CO$ at ${210^o}$under pressure
B) heating glycerol with oxalic acid at a high temperature
C) catalytic oxidation of ethane in presence of a catalyst
D) heating lead formulate in a current of hydrogen sulphide

Answer 1

Hint: When we say anhydrous it basically means a substance that has no water content in it. So now in this question, we have asked to prepare anhydrous formic acid so the reaction should be in such a way that there won’t be any production of a water molecule in the product.

Complete step-by-step answer:
A) Anhydrous formic acid has a chemical formula of $HCOOH$. When $NaOH$is heated with $CO$under pressure at a temperature of ${210^o}$ the reaction is
$CO + NaOH\xrightarrow[{{{210}^o}}]{{under{\text{ pressure}}}}HCOONa$ where $HCOONa$is known as sodium formate. So, the option cannot be true.
B) Heating of glycerol with oxalic acid at a high temperature which is around $503K$it gives us allyl alcohol and it also gives us water molecules. Hence, we can eliminate option B as well.
C) In catalytic oxidation of ethane water molecule is released as a by-product so again this cannot form anhydrous formic acid.
D) In the reaction of lead formulate with hydrogen sulphide when it is heated we get precipitate of lead and anhydrous formic acid.
$Pb{(HCOO)_2} + {H_2}S \to Pb \downarrow + 2HCOOH$

Hence, the correct answer is option ‘D’.

Note: Formic acid is a simplest carboxylic acid. It is basically used as a preservative. Apart from that, it is used as an antibacterial agent in livestock feed. Sodium hydroxide is used to neutralise formic acid. When ant stings the human body they insert some amount of formic acid.