When sodium reacts with cold water, then the product formed will be ___________.

When sodium reacts with cold water, then the product formed will be sodium hydroxide.
Sodium is a very reactive metal, and it is present at the top of the reactivity series. When sodium metal is reacted with cold water, it forms sodium hydroxide as a product which is a very strong base. Its reaction is given as
$2\mathit{Na}+2H_2\mathit{O }\to 2\mathit{NaOH}+H_2$