Write the reaction equations: СН3ОН → НСНО → НСООН.

Let’s write down the equations for organic substances:
CH3 – OH + CuO = HCHO + Cu + H2O – oxidation of methyl alcohol with copper oxide when heated, the reaction is qualitative for alcohol, in the process copper and formaldehyde are released;
НСНО + Ag2O = HCOOH + 2Ag – formaldehyde is oxidized with silver oxide when heated, silver and formic acid are released.
These reactions confirm the connection between alcohols, aldehydes and carboxylic acids. Formic acid is used in medicine for the treatment of rheumatism.