Question

When hydrochloric acid mixed with sodium hydroxide which reaction takes place.?

Answer 1

$HCl + NaOH$  ⇒  $NaCl + H_{2}O$
When hydrochloric acid (HCl) is mixed with sodium hydroxide (NaOH) , sodium chloride or common salt (NaCl) and water ($H_{2}O$) are formed. This reaction is a neutralization reaction, in which an acid and a base react to form a salt and water. 

Hope this may help you. 

Answer 2

It is an acid base reaction.
Neutralisation reaction takes place.
Products formed are NaCl (salt) and H₂O (water)

Balanced chemical equation:
HCl + NaOH → NaCl + H₂O