how are alcohols formed?
a) Addition of hydrogen in the presence of catalysts like finely divided platinum, palladium, nickel and ruthenium.
This method is called catalytic hydrogenation.
b) Treatment with chemical reagents such as sodium borohydride (NaBH4) or Lithium aluminium hydride (LiAlH4).
Aldehydes yield primary alcohols while ketones give secondary alcohols.
We hope that clarifies your query.